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In article <dei68b$apt$>, Dave Martindale
<> writes
> writes:
>
>>The camera will use a regulator(s) to supply the various circuits inside
>>it with power. If it is a simple linear reg. then it will run warmer
>>with a higher battery voltage because it has to drop more volts, the
>>current is unaltered although it is taking higher power from the
>>battery. If it is a switching reg. then for higher a battery voltage
>>the input current will reduce thus maintaining a consistent power
>>dissipation in the reg. and power consumption from the battery. Since
>>switching regs are much more efficient and can operate where the input
>>is less than the required output (or both +ve & -ve lines are required)
>>they are preferentially used.
>
>For the electronics power, you're probably right. But the electronic
>flash circuitry probably does not go through the regulator, because the
>current demand is so high and because the supply voltage doesn't need to
>be regulated. Similarly, motors may be powered directly from the supply
>voltage instead of regulated power.

Whilst the inverter for the flash is unlikely to be regulated I would be
astonished if the motors which need precise control are not.

--
Ian G8ILZ

On Wed, 24 Aug 2005 12:15:57 -0400, Bob Salomon wrote:

> Sea and Sea were selling electronic flash units for Scuba that were not
> vented properly for NiMh cells. If one used NiCd cells everything was
> fine. But some users of NiMh cells had their flash explode during use.
>
> Today their strobe are vented for NiMh cells but you should always check
> with the manufacturer of the item you want to use why they specifically
> tell you to use a specific type of cell.

Why is that? Though NiCad cells have lower capacity, they have
lower internal resistance and should be able to deliver greater
currents than NiMh cells of the same size and type. But then I'm
not sure if you're referring to venting of heat or something else.

writes:

>>Similarly, motors may be powered directly from the supply
>>voltage instead of regulated power.

>Whilst the inverter for the flash is unlikely to be regulated I would be
>astonished if the motors which need precise control are not.

Most motor control circuits achieve precise control of motors without
voltage regulation of the drive power.

Stepper motor drivers achieve precise control of position via the
frequency of the drive waveform, and may also control torque through
current control - while using an unregulated DC supply.

Servo motors use encoder feedback from the motor for precise control of
position.

DC motors can use encoder feedback, open-circuit voltage, or current
measurement to maintain nearly constant speed under load - all without
regulated supply voltage. This type of control works better than
simply supplying regulated voltage to the motor because it compensates
for load.

Basically, while motors *can* be driven from regulated voltage, they are
traditionally powered from the unregulated power bus because it
drastically reduces the size of the regulated power supply needed.

Dave

In article <>,
ASAAR <> wrote:

> if you're referring to venting of heat or something else.

Outgassing from the cell during use.

--
To reply no_ HPMarketing Corp.

Pete D <> wrote:

>"Joseph Meehan" <> wrote in message
>news:IxPOe.43918$. ..
>> ASAAR wrote:
>>> On Tue, 23 Aug 2005 19:57:27 -0400, Morton Linder wrote:
>>>
>>>> An earlier discussion of Lithium AA cells regarding film cameras a
>>>> few years ago revealed that, due to lower internal resistance, Li
>>>> cells can deliver a higher current flow (same voltage) which can
>>>> heat up and
>>>> destroy some sensitive electronic components.
>>>
>>> Absolutely not true. At a given voltage (under load), the camera
>>> will draw the same current, whether the source is alkaline or
>>> lithium, whether they are AAA, AA, C or D cells.
>>
>> But the issue is it appears that Lithium batteries deliver a higher
>> voltage under load, and therefore have the potential to deliver more
>> current.

>And therefore the higher voltage should equate to lower current!

All this speculation...

The bottom line is this: if the manufacturer says
don't use a certain type or types of batteries, then
DON'T DO IT.

Who knows why? Maybe they just don't like the brand,
but I'd not bet on it.

----- Paul J. Gans

In article <deij2f$dps$>, Dave Martindale
<> writes
> writes:
>
>>>Similarly, motors may be powered directly from the supply
>>>voltage instead of regulated power.
>
>>Whilst the inverter for the flash is unlikely to be regulated I would be
>>astonished if the motors which need precise control are not.
>
>Most motor control circuits achieve precise control of motors without
>voltage regulation of the drive power.

I did not mean that they could not be, in fact I would never rely on the
supply voltage for control.

>Stepper motor drivers achieve precise control of position via the
>frequency of the drive waveform, and may also control torque through
>current control - while using an unregulated DC supply.

Sorry, but precise control of position depends on the number of pulses,
the frequency (more properly pulse rate) determines the rate of change
of position.

>Servo motors use encoder feedback from the motor for precise control of
>position.

Have you considered the time constant of the loop and the effect due to
fluctuations in supply voltage.

>DC motors can use encoder feedback, open-circuit voltage, or current
>measurement to maintain nearly constant speed under load - all without
>regulated supply voltage. This type of control works better than
>simply supplying regulated voltage to the motor because it compensates
>for load.

Obviously.

>Basically, while motors *can* be driven from regulated voltage, they are
>traditionally powered from the unregulated power bus because it
>drastically reduces the size of the regulated power supply needed.

The kit we designed with stepper motors always used a regulated supply,
it gives a better engineering control and enhanced operating life.
--
Ian G8ILZ

writes:

>>Stepper motor drivers achieve precise control of position via the
>>frequency of the drive waveform, and may also control torque through
>>current control - while using an unregulated DC supply.

>Sorry, but precise control of position depends on the number of pulses,
>the frequency (more properly pulse rate) determines the rate of change
>of position.

Sophisticated stepper drivers synthesise sine waves with a phase shift
of 90 degrees (or 120, depending on the numbers of coils in the motor),
while simpler drivers use square waves. It makes sense to talk about
frequency and phase of both sine and square waves, while "pulse rate"
just seems wrong in the context of sine waves. Basically, the motor is
a synchronous motor rotating in lock-step with the input signal, whether
sine or square. If you want to be precise, speed is determined by
frequency, and position is determined by the integral of frequency.

>>Servo motors use encoder feedback from the motor for precise control of
>>position.

>Have you considered the time constant of the loop and the effect due to
>fluctuations in supply voltage.

As long as the servo amplifier has enough feedback, the output voltage
is pretty much independent of input voltage as long as the latter
remains within limits.

>The kit we designed with stepper motors always used a regulated supply,
>it gives a better engineering control and enhanced operating life.

And all of the stepper-drive systems I've seen did not need a regulated
supply for proper operation. If you're building a mains-operated device
and don't mind wasting some space and energy, regulating the stepper
drive voltage probably makes sense. But if you're trying for minimum
space and power, it makes sense to avoid regulating any supply you don't
need to.

Dave