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S110 - Cannot drive by lab power supply?

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Re: S110 - Cannot drive by lab power supply?
« Reply #30 on: 05 / May / 2015, 00:41:25 »
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CHDK is a hack operating outside Canon specifications.

I have seen too many people destroy electronic equipment through hacking.

Both circuits may work on normal DC or AC loads. The negative on modern electronics is the earth reference. Placing a resistor in series in the camera negative power supply line lifts the earth reference above the true negative generating artefacts in the negative rail. In many switched mode regulators lifting the negative reference above the true negative creates artefacts and possible self destruction.

Sorry; I am not contributing to possible camera damage.

The safe way to determine current draw is:

Establish the minimum and maximum voltages the camera will reliably operate by reading the manufacturer’s specifications. Once the minimum and maximum voltages are established and the recommended power supply is known, use hook-up cables capable of supplying twice the maximum constant current to eliminate voltage drop.

Connect a digital amp meter or a digital multimeter set to DC amps in series in the positive power line source and the camera positive. The negative is connected directly to negative. The current draw observed is the true constant current draw not the intermittent current draw. It is the maximum constant current draw that counts, the intermittent current draw will be taken care of by the internal filter capacitors. That is their function to supply peak intermittent loads.
« Last Edit: 05 / May / 2015, 00:44:49 by thepanoguy »

Re: S110 - Cannot drive by lab power supply?
« Reply #31 on: 05 / May / 2015, 08:23:43 »
CHDK is a hack operating outside Canon specifications.
CHDK is a software hack.  Using CHDK has no bearing on the topic being discussed here.

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I have seen too many people destroy electronic equipment through hacking.
Of course.  That's always one of the risks of  hacking.

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Placing a resistor in series in the camera negative power supply line lifts the earth reference above the true negative generating artifacts in the negative rail. In many switched mode regulators lifting the negative reference above the true negative creates artifacts and possible self destruction.
Artifacts?  I don't think so with this setup.

The camera is a completely floating load. Simple physics / electronics  says it does not see anything but the voltage across its battery terminals  It has no idea where it is relative to earth reference.  The same goes for the power supply  -  all it sees is the load across its output terminals.  As long as nothing in the load is grounded,  the physics is again simple.

However,  once you start talking about multiple cameras interconnected via USB cables and multiple switching power supplies,  all bets are off.  As I have pointed out many times on this forum when discussing multi-camera rigs, proper grounding is critical.  There are even potential life safety issues as one forum poster discovered.


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Sorry; I am not contributing to possible camera damage.
Noted.

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The safe way to determine current draw is:

Establish the minimum and maximum voltages the camera will reliably operate by reading the manufacturer’s specifications. Once the minimum and maximum voltages are established and the recommended power supply is known, use hook-up cables capable of supplying twice the maximum constant current to eliminate voltage drop.

Connect a digital amp meter or a digital multimeter set to DC amps in series in the positive power line source and the camera positive. The negative is connected directly to negative. The current draw observed is the true constant current draw not the intermittent current draw. It is the maximum constant current draw that counts, the intermittent current draw will be taken care of by the internal filter capacitors. That is their function to supply peak intermittent loads.
An excellent description.  But it will not tell you anything useful here.   

The OP has already shown that the power supply can deliver the rated load into a fixed resistance.  Yet it does not work powering his camera.  He has a transient condition occurring on start up and doing a bunch of average current measurements with even the most expensive DVM is not going to help diagnose that.   Watching the actual current flow by measuring differential voltae drop across his series low ohm resistor might let him see what is happening - especially if he compares it to battery power.

Having said all that,  my preference would have also been to place the series resistor in the positive leg of the circuit .  That's just good practice because, while not strictly needed for this simple setup, it will pay off the minute you add anything else that might be grounded to the circuit while experimenting with it.   Which is exactly what I believe you are concerned about too? Unfortunately,  the OP seems to be having difficulty understanding how to operate the scope in differential mode so he is using a negative leg configuration and connecting the scope ground to power supply ground.
« Last Edit: 05 / May / 2015, 09:00:16 by waterwingz »
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