External Power Source

Discussion in 'Digital Photography' started by Donald Gray, Oct 27, 2003.

  1. Donald Gray

    Donald Gray Guest

    In an earlier post, I made enquiries re external power sources for
    digital cameras. In Particular, the Nikon Coolpix 5700.

    I have now built up and bench tested a small regulated (stabilised)
    unit that gives me 8.4 volts at 1.5 amps. It uses an LM317 regulator
    chip.

    The unit can be very easily adjusted to give a stabilised output of
    any voltage up to 28 volts. Rather than use a 'fixed potentiometer' to
    set the voltage out, I opted for using 2 resistors. That way the
    voltage cannot accidently be altered!

    The total cost of the project was 8UKPounds. That was buying a kit
    set that had all the components in one bag, including an etched PCB.
    (saved hunting amongst the junk box of the bits!) All I had to do was
    throw the pot into the junk box and supply 2 resistors.

    The PCB measures 1.5" x 2" ( 50mm x 38mm) The whole thing fits neatly
    into a miniature die cast box 60x55x30mm (UK: Radio Spare part #
    225-142)

    I any one is interested, I can supply the circuit diagram (Public
    Domain from the chip manufacturer) together with the resistor values
    to give any voltage output. The primary source voltage needs to be 2.5
    volts or more, higher than the output voltage.

    I have not yet tried it in the camera as at the moment I am not sure
    an external psu can be used in the camera WITH the battery in situ or
    if the battery MUST be removed first.

    Can anyone advise please?
    --
    Donald Gray
    Putting ODCOMBE on the Global Village Map!
    www.odcombe.demon.co.uk
    You do not have to email me, but if you wish to...
    Please remove the SafetyPin from my email address first
    Thanks
    Donald Gray, Oct 27, 2003
    #1
    1. Advertising

  2. Donald, all,

    just wanted to remark on the sidelines that some cameras already
    have this function. The Panasonic Lumix DMC-FZ1, for example,
    comes with a thin little cable that connects to the external
    battery charger and supplies the camera with power while the
    battery is in the charger. (In fact the charger delays charging
    the battery while it has to supply electricity to the camera,
    but as soon as you switch off or disconnect the camera, it
    resumes charging.)

    I don't know whether that is a widespread or a rare feature, but
    it makes eminent sense when you come home with a fully
    discharged battery and want to download your pictures safely.
    Without this feature you would have some kind of a functional
    gap in this particular situation, which can conceivably occur
    from time to time.

    Hans-Georg

    --
    No mail, please.
    Hans-Georg Michna, Oct 27, 2003
    #2
    1. Advertising

  3. Donald Gray

    Donald Gray Guest

    On Mon, 27 Oct 2003 12:32:12 +0100, Hans-Georg Michna
    <> wrote:

    >Donald, all,
    >
    >just wanted to remark on the sidelines that some cameras already
    >have this function. The Panasonic Lumix DMC-FZ1, for example,
    >comes with a thin little cable that connects to the external
    >battery charger and supplies the camera with power while the
    >battery is in the charger. (In fact the charger delays charging
    >the battery while it has to supply electricity to the camera,
    >but as soon as you switch off or disconnect the camera, it
    >resumes charging.)
    >
    >I don't know whether that is a widespread or a rare feature, but
    >it makes eminent sense when you come home with a fully
    >discharged battery and want to download your pictures safely.
    >Without this feature you would have some kind of a functional
    >gap in this particular situation, which can conceivably occur
    >from time to time.
    >
    >Hans-Georg

    Thank you for the comments. The Nikon 5700 is supplied with an ac
    charger that cannot be also plugged into the camera. However the what
    I am trying to achieve is two fold.

    1) To purchase a 'branded' external battery adaptor is expensive. A
    home made one, properly designed and constructed is not.

    2) I want a voltage stabiliser that will take a variety of different
    power sources. I don't care (at this moment) if the external power
    source charges the camera's own battery. All I want to do is to be
    able to power the camera from external batteries such as a 12v bank of
    nicads, or dry cells, sealed lead acid or even a car battery.
    (Although a car battery clipped on the belt will spoil the cut of the
    trowsers somewhat!)

    The battery in the Nikon Coolpix 5700 battery has a duration of about
    90 minutes. Yes, I could buy more Nikon batteries, but branded
    products cost a lot more. Not only that, it will still have a duration
    of 90 minutes. Yes, I know 2 x 90 = 180 mins but that is not the
    point.

    There are times when I do not have access to recharging facilities
    but could have access to dry cells or nicads etc. Often I will need a
    lot more than 90 minutes without having to constantly power down the
    camera to conserve power, hence the project.

    BTW, I always recharge the camera's internal battery every time I have
    used it, even if I have only taken a few shots.
    --
    Donald Gray
    Putting ODCOMBE on the Global Village Map!
    www.odcombe.demon.co.uk
    You do not have to email me, but if you wish to...
    Please remove the SafetyPin from my email address first
    Thanks
    Donald Gray, Oct 27, 2003
    #3
  4. Donald Gray

    DHB Guest

    Donald,
    since you seem to know electronics well enough to build your
    own regulated power supply for your camera I will add my 2 cents worth for
    your consideration.

    Safety is always my 1st concern both personally & with regard to my
    electronic equipment. If you have not already done so you may want to add
    an over-voltage protection circuit into your power supply just is case the
    regulator IC shorts out (unlikely but it does happen).

    There are lots of ways to do this but among the simplest is to fuse the
    output & place an over-voltage "crowbar" circuit on the output after the
    fuse which will blow the fuse if the voltage rises above X preset level,
    thus saving your camera at the expense of the fuse.

    This can be as simple as a zener diode & resister or add an SCR to the
    circuit to make it more reliable. This may be overkill for something that
    happens so really but I bring it up only because you expressed concern about
    using variable resistor to set the output voltage & opted for a fixed
    resistor in it's place which I agree with for a fixed use, fixed voltage
    power supply.

    It may be overkill or over-engineering but I just thought I would offer
    this over-voltage protection option for your consideration. Best of luck &
    don't forget a good heatsink on the LM317 regulator also. Did not do the
    math but you may also wish to consider limiting the input voltage to your
    regulator IC or it's going to have a lot of heat to dissipate to maintain
    8.4VDC when supplying 1.5 Amperes.

    Hope this is of value.

    DHB

    "Donald Gray" <> wrote in message
    news:...
    > In an earlier post, I made enquiries re external power sources for
    > digital cameras. In Particular, the Nikon Coolpix 5700.
    >
    > I have now built up and bench tested a small regulated (stabilised)
    > unit that gives me 8.4 volts at 1.5 amps. It uses an LM317 regulator
    > chip.
    >
    > The unit can be very easily adjusted to give a stabilised output of
    > any voltage up to 28 volts. Rather than use a 'fixed potentiometer' to
    > set the voltage out, I opted for using 2 resistors. That way the
    > voltage cannot accidently be altered!
    >
    > The total cost of the project was 8UKPounds. That was buying a kit
    > set that had all the components in one bag, including an etched PCB.
    > (saved hunting amongst the junk box of the bits!) All I had to do was
    > throw the pot into the junk box and supply 2 resistors.
    >
    > The PCB measures 1.5" x 2" ( 50mm x 38mm) The whole thing fits neatly
    > into a miniature die cast box 60x55x30mm (UK: Radio Spare part #
    > 225-142)
    >
    > I any one is interested, I can supply the circuit diagram (Public
    > Domain from the chip manufacturer) together with the resistor values
    > to give any voltage output. The primary source voltage needs to be 2.5
    > volts or more, higher than the output voltage.
    >
    > I have not yet tried it in the camera as at the moment I am not sure
    > an external psu can be used in the camera WITH the battery in situ or
    > if the battery MUST be removed first.
    >
    > Can anyone advise please?
    > --
    > Donald Gray
    > Putting ODCOMBE on the Global Village Map!
    > www.odcombe.demon.co.uk
    > You do not have to email me, but if you wish to...
    > Please remove the SafetyPin from my email address first
    > Thanks
    DHB, Oct 27, 2003
    #4
  5. Donald Gray

    Lionel Guest

    Donald Gray <> wrote in message news:<>...
    > In an earlier post, I made enquiries re external power sources for
    > digital cameras. In Particular, the Nikon Coolpix 5700.
    >
    > I have now built up and bench tested a small regulated (stabilised)
    > unit that gives me 8.4 volts at 1.5 amps. It uses an LM317 regulator
    > chip.
    >
    > The unit can be very easily adjusted to give a stabilised output of
    > any voltage up to 28 volts. Rather than use a 'fixed potentiometer' to
    > set the voltage out, I opted for using 2 resistors. That way the
    > voltage cannot accidently be altered!
    >
    > The total cost of the project was 8UKPounds. That was buying a kit
    > set that had all the components in one bag, including an etched PCB.
    > (saved hunting amongst the junk box of the bits!) All I had to do was
    > throw the pot into the junk box and supply 2 resistors.
    >
    > The PCB measures 1.5" x 2" ( 50mm x 38mm) The whole thing fits neatly
    > into a miniature die cast box 60x55x30mm (UK: Radio Spare part #
    > 225-142)
    >
    > I any one is interested, I can supply the circuit diagram (Public
    > Domain from the chip manufacturer) together with the resistor values
    > to give any voltage output. The primary source voltage needs to be 2.5
    > volts or more, higher than the output voltage.
    >
    > I have not yet tried it in the camera as at the moment I am not sure
    > an external psu can be used in the camera WITH the battery in situ or
    > if the battery MUST be removed first.
    >
    > Can anyone advise please?


    Your knowledge of electronics is pathetic
    Lionel, Oct 27, 2003
    #5
  6. Donald Gray

    Donald Gray Guest

    On 27 Oct 2003 15:22:33 -0800, (Lionel) wrote:

    >Donald Gray <> wrote in message news:<>...
    >> In an earlier post, I made enquiries re external power sources for
    >> digital cameras. In Particular, the Nikon Coolpix 5700.
    >>
    >> I have now built up and bench tested a small regulated (stabilised)
    >> unit that gives me 8.4 volts at 1.5 amps. It uses an LM317 regulator
    >> chip.
    >>
    >> The unit can be very easily adjusted to give a stabilised output of
    >> any voltage up to 28 volts. Rather than use a 'fixed potentiometer' to
    >> set the voltage out, I opted for using 2 resistors. That way the
    >> voltage cannot accidently be altered!
    >>
    >> The total cost of the project was 8UKPounds. That was buying a kit
    >> set that had all the components in one bag, including an etched PCB.
    >> (saved hunting amongst the junk box of the bits!) All I had to do was
    >> throw the pot into the junk box and supply 2 resistors.
    >>
    >> The PCB measures 1.5" x 2" ( 50mm x 38mm) The whole thing fits neatly
    >> into a miniature die cast box 60x55x30mm (UK: Radio Spare part #
    >> 225-142)
    >>
    >> I any one is interested, I can supply the circuit diagram (Public
    >> Domain from the chip manufacturer) together with the resistor values
    >> to give any voltage output. The primary source voltage needs to be 2.5
    >> volts or more, higher than the output voltage.
    >>
    >> I have not yet tried it in the camera as at the moment I am not sure
    >> an external psu can be used in the camera WITH the battery in situ or
    >> if the battery MUST be removed first.
    >>
    >> Can anyone advise please?

    >
    >Your knowledge of electronics is pathetic


    ..... and your knowledge of courtesy is worse. Not only that, your
    inept response is incredibly rude and shows a gross lack of care and
    tolerances for others. I suggest you read the Desiderata (Do a Google
    search - seek and ye shall find.) If you can not find it, I will be
    happy to email you a copy.

    I would have expected something more from one of the most vociferous
    and prolix members of this ng.

    I asked a question in genuine quest of knowledge from those who do
    know more than me. Unfortunately we don't all have the inferred
    superior knowledge as you.

    I am an ex professional photographer with IBP qualifications. I am
    also a qualified electronics engineer. That said, the ravages of time
    have affected my memory and lack of using my photographic and
    electronic experience has diminished the ability somewhat.

    I sincerely hope, Lionel Bum, when you get to my age, you do not
    experience the loss of memory.

    I retired from Professional photography in 1968ish when colour was
    very expensive, Electronic Flash kit was driven by 250 volt batteries
    (Clive Courtney 'Langham' 150 joule) or wet cells with multivibrator
    voltage multipliers.

    It is many years since I did any electronic work....

    Recently, I indulged in buying a digicam. I fast realised that all of
    my knowledge was very much out of date. (And so was some of my
    treasured ancient kit!) I need to get up to speed with things. I shall
    continue to show my lack of knowledge by asking questions. That is how
    we learn.

    My offer to share the knowledge that I have garnered from this ng and
    my searches was out of a want of helping others who also may be
    interested in this particular subject.

    Believe it or not, Lionel Bum, there was a time when your knowledge of
    ALL things was non-existant (I refrain from using the word 'pathetic')

    Perhaps Mr Bum, If you genuinely believe my electronics knowledge is
    pathetic (which I already know because you have told me so) , perhaps
    you would be kind enough to furnish the answers or corrections to my
    pleas.

    Mr Bum, you must be very astute. How did you deduce that my level of
    electronics was pathetic from my posting?

    Fortunately, there *are* many courteous and helpful folk out there who
    can and do give that helping hand. To them, I give a warm vote of
    thanks.



    so mote it be! ;-)
    G3YPL/ ex ZL1AZC, JV7Z, KX4A etc
    RN2761 UGLE
    --
    Donald Gray
    Putting ODCOMBE on the Global Village Map!
    www.odcombe.demon.co.uk
    You do not have to email me, but if you wish to...
    Please remove the SafetyPin from my email address first
    Thanks
    Donald Gray, Oct 28, 2003
    #6
  7. Donald Gray

    Donald Gray Guest

    On Mon, 27 Oct 2003 18:43:56 GMT, "DHB" <> wrote:

    >Donald,
    > since you seem to know electronics well enough to build your
    >own regulated power supply for your camera I will add my 2 cents worth for
    >your consideration.
    >
    > Safety is always my 1st concern both personally & with regard to my
    >electronic equipment. If you have not already done so you may want to add
    >an over-voltage protection circuit into your power supply just is case the
    >regulator IC shorts out (unlikely but it does happen).
    >
    > There are lots of ways to do this but among the simplest is to fuse the
    >output & place an over-voltage "crowbar" circuit on the output after the
    >fuse which will blow the fuse if the voltage rises above X preset level,
    >thus saving your camera at the expense of the fuse.
    >
    > This can be as simple as a zener diode & resister or add an SCR to the
    >circuit to make it more reliable. This may be overkill for something that
    >happens so really but I bring it up only because you expressed concern about
    >using variable resistor to set the output voltage & opted for a fixed
    >resistor in it's place which I agree with for a fixed use, fixed voltage
    >power supply.
    >
    > It may be overkill or over-engineering but I just thought I would offer
    >this over-voltage protection option for your consideration. Best of luck &
    >don't forget a good heatsink on the LM317 regulator also. Did not do the
    >math but you may also wish to consider limiting the input voltage to your
    >regulator IC or it's going to have a lot of heat to dissipate to maintain
    >8.4VDC when supplying 1.5 Amperes.


    Yoda2K
    Thanks for the suggestion - it had not crossed my mind to add OV
    protection. Will do.

    My intended source supply will be a 12 sealed lead acid gell battery.
    I am hoping to share the battery with the Braun F80 flash unit and use
    it as an emergency supply for the camera if & when I find myself with
    a flat camera battery. There will be a minimum volts drop. The Camera
    is rated as 0.9a & I would think that is during the flash recharging
    time. Although I cannot be sure until i try it for real, I don't
    believer the power dissipation to be a problem. However, I have
    utilised a heat sink, just in case. The psu is in a small diecast box
    & I could use that as a much bigger heat sink if needed.

    regards

    --
    Donald Gray
    Putting ODCOMBE on the Global Village Map!
    www.odcombe.demon.co.uk
    You do not have to email me, but if you wish to...
    Please remove the SafetyPin from my email address first
    Thanks
    Donald Gray, Oct 28, 2003
    #7
  8. Donald Gray

    Lionel Guest

    Word has it that on Tue, 28 Oct 2003 10:42:48 +0000, in this august
    forum, Donald Gray <> said:

    >On 27 Oct 2003 15:22:33 -0800, (Lionel) wrote:
    >>Your knowledge of electronics is pathetic

    >
    >.... and your knowledge of courtesy is worse. Not only that, your
    >inept response is incredibly rude and shows a gross lack of care and
    >tolerances for others. I suggest you read the Desiderata (Do a Google
    >search - seek and ye shall find.) If you can not find it, I will be
    >happy to email you a copy.
    >
    >I would have expected something more from one of the most vociferous
    >and prolix members of this ng.


    Donald,

    Just letting you know that your reply was to one of the trolls, not to a
    genuine poster here. He's a attention-seeking child who posts only to
    encourage responses from real people. It's usually best to ignore such
    posts, or silently report them to the news service that the troll's
    posting from ( in this case).

    In response to your original question:
    -------------
    >I have now built up and bench tested a small regulated (stabilised)
    >unit that gives me 8.4 volts at 1.5 amps. It uses an LM317 regulator
    >chip.


    One important tip with the LM317: Bear in mind that the full output
    current (1.5A - I assume you're using either the TO-3 or TO-220 version)
    is only available with good heatsinking. You need enough heatsinking to
    keep the die temperature (in the spec sheet) below its rated maximum, or
    the regulator will automatically shutdown to keep the chip from failing.
    You can determine the maximum power dissipation in Watts by subtracting
    the output voltage from the input voltage & multiplying by the current
    drain of your load (Pdiss = (Vin - Vout) x Iload). If you check the fine
    print on the LM317K spec sheet, you'll find that the power rating on the
    bare regulator is actually very small, & will require heatsinking for
    any reasonable sort of load. Either way, it'll need air flow at the very
    least. If you start finding that the camera shuts down after being used
    happily for a short while, the regulator is probably going into thermal
    shutdown, due to overheating.

    (Yes, I have designed & built a lot of linear supplies in my life, how
    could you tell? ;)

    >The unit can be very easily adjusted to give a stabilised output of
    >any voltage up to 28 volts. Rather than use a 'fixed potentiometer' to
    >set the voltage out, I opted for using 2 resistors. That way the
    >voltage cannot accidently be altered!


    Yep. I built a similar supply many years ago as an adapter for random
    electronic devices, & solved that problem by using a multiturn trimmer,
    which can only be adjusted with a screwdriver.

    >I have not yet tried it in the camera as at the moment I am not sure
    >an external psu can be used in the camera WITH the battery in situ or
    >if the battery MUST be removed first.


    >Can anyone advise please?


    I'm not familiar with your particular camera, so I can't give you a
    definitive answer. OTOH, it should be easy to find out. If your camera
    has a power socket, your manual should state whether it's safe to use
    external power with batteries installed or not. If you're actually
    modifying the camera to use an external supply (ie; drilling a hole in
    the case & running a cable into the power rails), then no, *do not* do
    use your external supply while the batteries are in the camera. You
    would run a very real risk of exploding your batteries and/or severely
    damaging your camera.
    This is not to say that it isn't possible to make it safe to use both
    at the same time, but it would require modification to both the supply &
    the wiring from the battery compartment. I would do it by buying two
    Schottky diodes (rated at 2 Amps, or heavier) & wiring one in series
    with the positive wire from the battery compartment, & wiring the other
    series with the external supply socket (or cable) in the same way. This
    would prevent either the batteries or the supply from applying a voltage
    to the other, & using Schottky diodes (0.1V voltage drop) in place of
    regular diodes (0.6V voltage drop) would prevent reduced battery life, &
    prevent the camera from getting confused by the lower battery voltage,
    which would likely make it think the batteries are flat when they're
    not.
    If you are comfortable with reading schematics & rewiring small devices,
    I could probably draw you a back-of-an-envelope circuit. If you're
    inexperienced, you should probably not tackle the job, as it would be
    extremely easy for you to destroy your camera, & I'd prefer not to have
    that on my conscience.

    Cheers!

    --
    W
    . | ,. w , "Some people are alive only because
    \|/ \|/ it is illegal to kill them." Perna condita delenda est
    ---^----^---------------------------------------------------------------
    Lionel, Oct 28, 2003
    #8
  9. Donald Gray

    Lionel Guest

    Word has it that on Mon, 27 Oct 2003 18:43:56 GMT, in this august forum,
    "DHB" <> said:

    >Donald,
    > since you seem to know electronics well enough to build your
    >own regulated power supply for your camera I will add my 2 cents worth for
    >your consideration.
    >
    > Safety is always my 1st concern both personally & with regard to my
    >electronic equipment. If you have not already done so you may want to add
    >an over-voltage protection circuit into your power supply just is case the
    >regulator IC shorts out (unlikely but it does happen).


    Yep, very true. The ground connection to the regulator common pin going
    open circuit is a really common cause of this, in my experience, &
    results in the regulator 'floating', & the output rising to nearly the
    input volatge.

    > There are lots of ways to do this but among the simplest is to fuse the
    >output & place an over-voltage "crowbar" circuit on the output after the
    >fuse which will blow the fuse if the voltage rises above X preset level,
    >thus saving your camera at the expense of the fuse.


    My cynical nature compels me to point out that crowbar circuits fail as
    often as regulators do, & fuses often blow more slowly than the
    expensive chips that they're supposed to be protecting. ;)
    That said, one good thing about the LM317 (et al) is that a crowbar
    circuit will throw them into overcurrent protection mode, often faster
    than a fuse will blow, so yes, a crowbar circuit would be a worthwhile
    addition, particularly if he's going to be running the supply from
    weird/noisy/spiky power sources. If he's going to hook it to random
    power sources, I'd also include polarity protection on the input, lots
    of decoupling cap's, & possibly a basic pre-regulator.

    > It may be overkill or over-engineering but I just thought I would offer
    >this over-voltage protection option for your consideration. Best of luck &
    >don't forget a good heatsink on the LM317 regulator also. Did not do the
    >math but you may also wish to consider limiting the input voltage to your
    >regulator IC or it's going to have a lot of heat to dissipate to maintain
    >8.4VDC when supplying 1.5 Amperes.


    Yes, exactly. 1.5A on a TO-3 or TO-220 equals a lot of heat. I've
    included the required maths in my follow-up to Donald's original post,
    which will hopefully help him select an appropriate heatsink, & convince
    him to mount it & the regulator externally, on a nice, solid diecast
    aluminium box.

    --
    W
    . | ,. w , "Some people are alive only because
    \|/ \|/ it is illegal to kill them." Perna condita delenda est
    ---^----^---------------------------------------------------------------
    Lionel, Oct 28, 2003
    #9
  10. Donald Gray

    Donald Gray Guest

    On Wed, 29 Oct 2003 01:20:33 +1100, Lionel <> wrote:
    []
    >
    >Just letting you know that your reply was to one of the trolls, not to a
    >genuine poster here. He's a attention-seeking child who posts only to
    >encourage responses from real people. It's usually best to ignore such
    >posts, or silently report them to the news service that the troll's
    >posting from ( in this case).


    []
    I know that now - I did a search for his other posts and realised I
    had been suckered in ....
    >In response to your original question:
    >-------------
    >>I have now built up and bench tested a small regulated (stabilised)
    >>unit that gives me 8.4 volts at 1.5 amps. It uses an LM317 regulator
    >>chip.

    >
    >One important tip with the LM317: Bear in mind that the full output
    >current (1.5A - I assume you're using either the TO-3 or TO-220 version)
    >is only available with good heatsinking.


    I am using a heat sink. but can increase the heat dissipation buy
    utilising the metal box the cct is in.

    > You need enough heatsinking to
    >keep the die temperature (in the spec sheet) below its rated maximum, or
    >the regulator will automatically shutdown to keep the chip from failing.
    >You can determine the maximum power dissipation in Watts by subtracting
    >the output voltage from the input voltage & multiplying by the current
    >drain of your load (Pdiss = (Vin - Vout) x Iload). If you check the fine
    >print on the LM317K spec sheet, you'll find that the power rating on the
    >bare regulator is actually very small, & will require heatsinking for
    >any reasonable sort of load. Either way, it'll need air flow at the very
    >least. If you start finding that the camera shuts down after being used
    >happily for a short while, the regulator is probably going into thermal
    >shutdown, due to overheating.


    Once I start to use it, I shall be monitoring the power dissipation
    very closely to ensure it is man enough for the job (If not, I have a
    neat little radio scanner that draws much less and has the same V
    needs and will start over using something a bit more beefy.)

    >(Yes, I have designed & built a lot of linear supplies in my life, how
    >could you tell? ;)


    It sorta shows a bit at the edges :=)
    >
    >>The unit can be very easily adjusted to give a stabilised output of
    >>any voltage up to 28 volts. Rather than use a 'fixed potentiometer' to
    >>set the voltage out, I opted for using 2 resistors. That way the
    >>voltage cannot accidently be altered!

    >
    >Yep. I built a similar supply many years ago as an adapter for random
    >electronic devices, & solved that problem by using a multiturn trimmer,
    >which can only be adjusted with a screwdriver.


    The only multi turn pot I have is a precision wound 10 turn that is
    almost bigger than the camera! but yes agreed if components readily at
    hand. I have a full range of E24 series resistors and with a fixed
    single use psu, it was safer using an R divider to set the reference
    voltage than a cheap 5k pot that could be knocked
    >
    >>I have not yet tried it in the camera as at the moment I am not sure
    >>an external psu can be used in the camera WITH the battery in situ or
    >>if the battery MUST be removed first.

    >
    >>Can anyone advise please?

    >
    > I'm not familiar with your particular camera, so I can't give you a
    >definitive answer. OTOH, it should be easy to find out. If your camera
    >has a power socket, your manual should state whether it's safe to use
    >external power with batteries installed or not.

    Yes it has a power socket - a standard type coaxial fitting and I have
    several correct plugs (a bonus). However, The book does not say about
    with or without battery. The reason I hesitate to do the deed and try
    it is that someone recently posted a story here about this very
    subject and 'locked' his camera up.... I cant remember full details
    but enough to make me a little more careful before I fry an expensive
    camera that is only a few days old....

    I am presuming that the info on how the external psu is to be used
    (with/without camera battery in situ) is in the instructions with the
    Nikon external psu.

    >If you're actually
    >modifying the camera to use an external supply (ie; drilling a hole in
    >the case & running a cable into the power rails), then no, *do not* do
    >use your external supply while the batteries are in the camera. You
    >would run a very real risk of exploding your batteries and/or severely
    >damaging your camera.


    No drilling. No mods. No unintentional charging of Ni-Ion bats (Anyone
    can make a big bang - the clever bit is not being there when it
    happens)
    > This is not to say that it isn't possible to make it safe to use both
    >at the same time, but it would require modification to both the supply &
    >the wiring from the battery compartment. I would do it by buying two
    >Schottky diodes (rated at 2 Amps, or heavier) & wiring one in series
    >with the positive wire from the battery compartment, & wiring the other
    >series with the external supply socket (or cable) in the same way. This
    >would prevent either the batteries or the supply from applying a voltage
    >to the other, & using Schottky diodes (0.1V voltage drop) in place of
    >regular diodes (0.6V voltage drop) would prevent reduced battery life, &
    >prevent the camera from getting confused by the lower battery voltage,
    >which would likely make it think the batteries are flat when they're
    >not.



    >If you are comfortable with reading schematics & rewiring small devices,
    >I could probably draw you a back-of-an-envelope circuit.

    Thank, I would appreciate that. I am very comfy with messing with
    small components. I have temperature controlled Iron and needle bits.

    > If you're
    >inexperienced, you should probably not tackle the job, as it would be
    >extremely easy for you to destroy your camera, & I'd prefer not to have
    >that on my conscience.
    >
    >Cheers!


    Lionel

    Thanks for the very interesting info. I shall re read the last bit and
    digest & it.

    One of the problems here (in the westcountry of UK) is that I am no
    longer in the Electronics Trade and can't just ring the suppliers and
    re-order components like I used to. There are no component suppliers
    within easy distance. I have to rely on my junk box, a few old pcbs
    from various scrapped commercial 2 way radios (My old business) and
    buying kitsets from Internet hobbiest outlets. Often I have to make do
    with what I have got.

    Anecdote: My Dad was an electronics buff back in the late 40s & 50s
    when it was almost impossible to buy components. I have actually seen
    him file a carbon resistor to a value he needed. And hand make
    capacitors. That was in the days when you could tell which valve was
    blown because it didn't glow any more!... Those were the days!


    --
    Donald Gray
    Putting ODCOMBE on the Global Village Map!
    www.odcombe.demon.co.uk
    You do not have to email me, but if you wish to...
    Please remove the SafetyPin from my email address first
    Thanks
    Donald Gray, Oct 28, 2003
    #10
  11. Donald Gray

    DHB Guest

    Lionel,
    your response to my post & added information for the Original
    Poster should prove quite helpful. Often when I offer electronic advice or
    suggestions on a newsgroup I try to Keep It Simple, my friends often need to
    remind of the "K.I.S.S." principle.

    With that said I agree about the speed of a fuse being a problem in the
    protection of many electronic circuits but I suggested it's use between the
    regulator IC & the crowbar O.V. circuit intentionally.

    <1> When the fuse blows it's very clear there may be a problem.

    <2> The blown fuse disconnects the power from the load.

    All of this just makes it easier & safer for somebody with less
    electronics knowledge to recognize & identify a circuit or component
    failure. It's not a perfect setup but is a reasonable 1 that provides good
    protection for his camera & it conforms to the K.I.S.S. principle.

    Having worked in the telecommunications field where reliability is
    achieved by overengeneering & redundancy, I have to limit my tendencies
    every time I build something just to keep the cost & time down to reasonable
    levels. Like I said, "my friends often need to remind of the "K.I.S.S."
    principle."

    The other thing I try to design in my projects is thought in how to make
    things "Fool Proof" because being human means we can & do make mistakes so I
    try to minimize my human error ability where possible. Things like using
    only polarized connectors / plugs, different size or type connectors when
    connecting many items so that I can't plug the wrong thing into the wrong
    place & cause a problem.

    Sometimes I will even go as far as to place a bridge rectifier in line
    with a DC input lead so that polarity to a device will always be correct
    regardless of the polarity of the DC input. A single diode would protect
    the device from the wrong polarity but it would not work with the wrong
    polarity but would with the bridge rectifier in line minus the voltage drops
    of course.

    My 2 cents & then some.

    Respectfully, DHB


    "Lionel" <> wrote in message
    news:...
    > Word has it that on Mon, 27 Oct 2003 18:43:56 GMT, in this august forum,
    > "DHB" <> said:
    >
    > >Donald,
    > > since you seem to know electronics well enough to build your
    > >own regulated power supply for your camera I will add my 2 cents worth

    for
    > >your consideration.
    > >
    > > Safety is always my 1st concern both personally & with regard to my
    > >electronic equipment. If you have not already done so you may want to

    add
    > >an over-voltage protection circuit into your power supply just is case

    the
    > >regulator IC shorts out (unlikely but it does happen).

    >
    > Yep, very true. The ground connection to the regulator common pin going
    > open circuit is a really common cause of this, in my experience, &
    > results in the regulator 'floating', & the output rising to nearly the
    > input volatge.
    >
    > > There are lots of ways to do this but among the simplest is to fuse

    the
    > >output & place an over-voltage "crowbar" circuit on the output after the
    > >fuse which will blow the fuse if the voltage rises above X preset level,
    > >thus saving your camera at the expense of the fuse.

    >
    > My cynical nature compels me to point out that crowbar circuits fail as
    > often as regulators do, & fuses often blow more slowly than the
    > expensive chips that they're supposed to be protecting. ;)
    > That said, one good thing about the LM317 (et al) is that a crowbar
    > circuit will throw them into overcurrent protection mode, often faster
    > than a fuse will blow, so yes, a crowbar circuit would be a worthwhile
    > addition, particularly if he's going to be running the supply from
    > weird/noisy/spiky power sources. If he's going to hook it to random
    > power sources, I'd also include polarity protection on the input, lots
    > of decoupling cap's, & possibly a basic pre-regulator.
    >
    > > It may be overkill or over-engineering but I just thought I would

    offer
    > >this over-voltage protection option for your consideration. Best of luck

    &
    > >don't forget a good heatsink on the LM317 regulator also. Did not do the
    > >math but you may also wish to consider limiting the input voltage to your
    > >regulator IC or it's going to have a lot of heat to dissipate to maintain
    > >8.4VDC when supplying 1.5 Amperes.

    >
    > Yes, exactly. 1.5A on a TO-3 or TO-220 equals a lot of heat. I've
    > included the required maths in my follow-up to Donald's original post,
    > which will hopefully help him select an appropriate heatsink, & convince
    > him to mount it & the regulator externally, on a nice, solid diecast
    > aluminium box.
    >
    > --
    > W
    > . | ,. w , "Some people are alive only because
    > \|/ \|/ it is illegal to kill them." Perna condita delenda est
    > ---^----^---------------------------------------------------------------
    DHB, Oct 28, 2003
    #11
  12. Donald Gray

    Donald Gray Guest

    On Wed, 29 Oct 2003 01:20:33 +1100, Lionel <> wrote:

    []
    >One important tip with the LM317: Bear in mind that the full output
    >current (1.5A - I assume you're using either the TO-3 or TO-220 version)
    >is only available with good heatsinking. You need enough heatsinking to
    >keep the die temperature (in the spec sheet) below its rated maximum, or
    >the regulator will automatically shutdown to keep the chip from failing.
    >You can determine the maximum power dissipation in Watts by subtracting
    >the output voltage from the input voltage & multiplying by the current
    >drain of your load (Pdiss = (Vin - Vout) x Iload). If you check the fine
    >print on the LM317K spec sheet, you'll find that the power rating on the
    >bare regulator is actually very small, & will require heatsinking for
    >any reasonable sort of load. Either way, it'll need air flow at the very
    >least. If you start finding that the camera shuts down after being used
    >happily for a short while, the regulator is probably going into thermal
    >shutdown, due to overheating.
    >[]

    Just to let you know, Lionel, I bit the bullet and powered up the
    camera and the following currents were measured.

    I don't have a 'scope so the flash readings are subjective.

    My temperature sensor was very scientific; A little finger (Left hand
    of course) placed on the heat sink.

    Camera: Nikon Coolpix 5700 WITHOUT it's internal battery
    Source power supply: 12 V regulated @1.5a

    Home brew (kitset modified slightly) stabiliser to 8.4v

    Current (Amps):
    1) On switch on = 0.5
    2) Camera focusing (servos running) = 0.46
    3) Camera on focus (No servos running) and button at half pressed =
    0.39
    4) Camera powered but quescent (Not focussing just sitting on desk, no
    buttons pressed) = 0.38
    5) About .1 of a second before flash firing = 1.5a but at a very short
    duration. Unable to measure time.


    I left the camera as at 4 above for 10 minutes constantly monitoring
    the heatsink. It got quite warm, not hot.

    After taking 10 flash photos in rapid succession the heat sink was a
    bit warmer but still not hot.

    Interesting...

    --
    Donald Gray
    Putting ODCOMBE on the Global Village Map!
    www.odcombe.demon.co.uk
    You do not have to email me, but if you wish to...
    Please remove the SafetyPin from my email address first
    Thanks
    Donald Gray, Oct 28, 2003
    #12
  13. Donald Gray

    Donald Gray Guest

    On Tue, 28 Oct 2003 17:21:35 GMT, "DHB" <> wrote:

    []
    >
    > With that said I agree about the speed of a fuse being a problem in the
    >protection of many electronic circuits but I suggested it's use between the
    >regulator IC & the crowbar O.V. circuit intentionally.
    >
    > <1> When the fuse blows it's very clear there may be a problem.
    >
    > <2> The blown fuse disconnects the power from the load.
    >
    > All of this just makes it easier & safer for somebody with less

    []
    > Sometimes I will even go as far as to place a bridge rectifier in line
    >with a DC input lead so that polarity to a device will always be correct
    >regardless of the polarity of the DC input.


    Another valuable contribution. Thanks.

    Indeed, I have a bridge rectifier on the input.

    --
    Donald Gray
    Putting ODCOMBE on the Global Village Map!
    www.odcombe.demon.co.uk
    You do not have to email me, but if you wish to...
    Please remove the SafetyPin from my email address first
    Thanks
    Donald Gray, Oct 28, 2003
    #13
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