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S110 - Cannot drive by lab power supply?

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Offline waterwingz

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Re: S110 - Cannot drive by lab power supply?
« Reply #20 on: 03 / May / 2015, 13:46:58 »
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Quote from: mr.burns on 03 / May / 2015, 13:20:50
@waterwingz: What gage are the wires between your power supply and how long are they?
These are typical wires for lab powersupplies, length 1m, diameter 4mm.
(something like this: https://www1.elfa.se/data1/wwwroot/assets/large/laborkabel-stift-4-mm-silikon-vergoldet-8.jpg)
These ones I used only to drive the cam by lab power supply.
But if you read further I used these cables also with my new power supply and there it works.
Those wires look good.  I just asked in case you were using something bad like 2 meters of 28 gage (0,3 mm)  wire wrap wire.

Quote
For comparision I bought a new lab power supply (Manson SSP-8160). And with this one I have no problems at all.
That pretty much points to either an issue with the old power supply or just some incompablity when driving an electronic devices that is expecting battery power (like a powershot camera).

Quote
But I am still interested what was happening so I did some measurements with my oscilloscope (Hameg HMO1022).
I used my rechargable batteries (3x1.2V) and a shunt resistor (copper cable 0.5mm diameter, length ca. 34 cm --> 0.095 Ohms). This shunt I put in series with my S110 and did a measurement of the voltage at the shunt in single-shot mode.
(screenshot see attached image). On my oscilloscope I zoomed to the trigger point and found a peak of around 60mV. Together with my shunt resistor of 0.1 Ohm I get a current of 600mA. I doubt that my Voltcraft Digi40 could not handle 600mA.
May this several peaks the Voltcraft Digi40 could not handle?
Is the attached image a picture of the current flow when using your batteries? (and not the power supply)?

If so,  what does it look like when you attach the older power supply?
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Offline mr.burns

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Re: S110 - Cannot drive by lab power supply?
« Reply #21 on: 03 / May / 2015, 15:01:20 »
Hi waterwingz,

> Is the attached image a picture of the current flow when using your batteries? (and not the power supply)?

Yes it is!

> If so,  what does it look like when you attach the older power supply?

I tried this, but since the voltage goes down to 1.7V the cam did not switch on - so I did not get anything to measure.

I also tried with the new Manson power supply, but since the base noise is much higher compared to the battery I could not trigger at 50mV but only at 130mV. And in case I could trigger I did not get any significant waveform compared to the one using the batteries. (see atached image)
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Offline mr.burns

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Re: S110 - Cannot drive by lab power supply?
« Reply #22 on: 03 / May / 2015, 15:13:18 »
Hi,

I made a mistake in my calculation, the resitance of my shunt resistor is 30 mOhms and not 100 mOhms.
So the current pulled was not 600mA but around 2.0 A.

But even if it is 2.0A my older Voltcraft Digi 40 could deliver 5.0A.

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Offline waterwingz

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Re: S110 - Cannot drive by lab power supply?
« Reply #23 on: 03 / May / 2015, 15:28:24 »
Quote from: mr.burns on 03 / May / 2015, 15:01:20
I tried this, but since the voltage goes down to 1.7V the cam did not switch on - so I did not get anything to measure.
Use your two channels in differential mode (i.e. one on each side of your series resistor with the B channed inverted and added to the A channel) and trigger when that signal changes.  You should be able to catch the camera startup that way and the signal should be quite interesting to see prior to it going to 1.7V ?

Quote from: mr.burns on 03 / May / 2015, 15:13:18
I made a mistake in my calculation, the resitance of my shunt resistor is 30 mOhms and not 100 mOhms.
So the current pulled was not 600mA but around 2.0 A.  But even if it is 2.0A my older Voltcraft Digi 40 could deliver 5.0A.
The issue isn't the DC current draw.  As several people have suggested,  it's how the control circuit in your old power supply handles a load like a camera with a wildly fluctuating current draw.  In the case of the old supply,  it just seems to "crowbar" (or something similiar) and shut down.
 
« Last Edit: 03 / May / 2015, 15:39:55 by waterwingz »
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Offline mr.burns

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Re: S110 - Cannot drive by lab power supply?
« Reply #24 on: 04 / May / 2015, 02:47:28 »
Quote
Use your two channels in differential mode (i.e. one on each side of your series resistor with the B channed inverted and added to the A channel) and trigger when that signal changes.  You should be able to catch the camera startup that way and the signal should be quite interesting to see prior to it going to 1.7V ?
Sorry - I don't understand this. What means 'on each side of series resistor'? My series resistor is just a thin copper cable length 34 cm. (see attached image)
And I don't know if my oscilloscope can trigger on a math value of two channels.

Quote
In the case of the old supply,  it just seems to "crowbar" (or something similiar) and shut down.
In this case the powersupply should shutdown if I switch on the camera - but as mentioned already, the camera is switched off. Just connecting the (switched off) camera to the power supply will cause it to go down to 1.7V but current shows 0.0A.
« Last Edit: 04 / May / 2015, 02:52:31 by mr.burns »
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Offline thepanoguy

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Re: S110 - Cannot drive by lab power supply?
« Reply #25 on: 04 / May / 2015, 06:04:50 »
@mrburns,

A shunt circuit is a circuit connected directly across the + and - terminals of the power supply. It’s purpose is to provide a load on the power supply.

The circuit diagram you posted is a series resistor circuit. By design it will limit the maximum current draw on the power supply. If the voltage and current supplied is not enough for the camera to function effectively, the camera will shut down.

The 1.7 volt drop you are reading on the camera negative lead when referenced to the negative terminal is the voltage drop across the resistor in the negative power line not the voltage supplied by the positive terminal of the power supply. Just looking at the circuit, I would say that 1.7 volt drop is shutting down your camera because of under-voltage and under current.

Some electrical fundamentals:

Your power supply should be set to the maximum output regulated voltage the camera is capable of handling, under no load. A purely resistive load capable of drawing full current should be connected across the power supply terminals. If the regulator is operating correctly, there should be no volt drop.

If the voltage is correct, the camera should be connected across the terminals, using cable capable of carrying 10 amps.

Danger Warning.

Connecting the power supply directly across the battery terminals with the batteries in the carrier will cause the batteries to heat up and possibly explode.

If the camera is connected correctly, the power supply shuts down, you have RF artefacts being injected into the regulator IC’s. You can verify it by connecting the oscilloscope probe across the + terminal and the earth clip on the - terminal, then switching on the camera. You should observe artefacts before the camera switches off.

If there are RF artefacts, the power supply IC’s need 0.1uf ceramic capacitors directly soldered onto the + and - pins of the regulator IC’s. If the shut-down persists the inputs of the IC’s are detecting, probably amplifying RF by the IC’s. Soldering 0.1uf ceramic capacitors on the input pins and - pins, output pins and - pins are required.

If there are still RF artefacts, the power supply design is incompatible with the camera switching regulator circuit.   

Unless you possess a through understanding of power supply design, don’t attempt the modifications. You can do some serious damage.
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Offline mr.burns

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Re: S110 - Cannot drive by lab power supply?
« Reply #26 on: 04 / May / 2015, 06:28:19 »
@thepanoguy,

Quote
The 1.7 volt drop you are reading on the camera negative lead when referenced to the negative terminal is the voltage drop across the resistor in the negative power line not the voltage supplied by the positive terminal of the power supply. Just looking at the circuit, I would say that 1.7 volt drop is shutting down your camera because of under-voltage and under current.

With my cable shunt of 30mOhm I measure the voltage on the shunt resistor - not the battery.
This I did to detect the peak current consumption during the switch on period of my S110.
It was not used to measure the voltage provided by the batteries!

The voltage provided by the battery I measured with my small voltage measuring device connected to the battery.

Attached you will find the modified image using batteries instead the power supply. This schema I used to measure the current peak during switch on period.
« Last Edit: 04 / May / 2015, 06:44:34 by mr.burns »
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Offline thepanoguy

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Re: S110 - Cannot drive by lab power supply?
« Reply #27 on: 04 / May / 2015, 10:23:17 »
In my part of the world, Perth, Western Australia I am a qualified electrician. Trying to diagnose your problem without seeing your set-up is difficult.

The overall issue is Canon do not disclose internal components. The genuine power supplies available for the camera are matched functional units. Trying to build and debug home brew electrical equipment is a time consuming challenge.

The only reliable method to measure current draw is using a digital amp meter to measure, observe the current draw. An oscilloscope will give you inaccurate false readings. The majority of cheap digital multi meters contain a DC amp range usually 10 amps.

The critical moment is start-up. The instant current surge to start the DC to DC switched mode regulator in the camera is an unknown factor. Batteries are capable of delivering very high currents for milliseconds enough for the regulator to deliver initial high burst currents to charge the filter capacitors.

https://en.wikipedia.org/wiki/Ohm%27s_law

You have a series resistance (the shunt in your drawing) in the power supply. You need to calculate the current draw through the resistance without the camera connected. What is the resistance value when measured with an ohm meter?

The same with the lab power supply. You need to direct connect without the shunt in your drawing.

You will get a more accurate reading just using the current setting on a digital multi meter. You can try both and compare the results.
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Offline waterwingz

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Re: S110 - Cannot drive by lab power supply?
« Reply #28 on: 04 / May / 2015, 10:39:24 »
Quote from: thepanoguy on 04 / May / 2015, 10:23:17
The only reliable method to measure current draw is using a digital amp meter to measure, observe the current draw. An oscilloscope will give you inaccurate false readings. The majority of cheap digital multi meters contain a DC amp range usually 10 amps.

You will get a more accurate reading just using the current setting on a digital multi meter. You can try both and compare the results.
I respectfully disagree with both of these statements.

Measuring voltage drop across a series resistor (albeit a very low ohm resistor)  with an 2 channel oscilloscope in differential mode is an excellent way to observe current flow during start-up.  I fail to see any possibility of "inaccurate false readings" if it is hooked up correctly.

As far any digital meter goes, that will give you an averaged reading of steady state current.  By the time the display even updates, the event will be over.  I fail to see any value in that.

Or am I missing something here?
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Offline mr.burns

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Re: S110 - Cannot drive by lab power supply?
« Reply #29 on: 04 / May / 2015, 14:40:33 »
Hi,

I did another measurement as suggested by waterwingz (see attached image).
This time I used again my older power supply Voltcraft Digi40 as power source.
I measured the timepoint (S110 switsched off!) when I connected the S110 to the Digi40.
I set the trigger level to 100mV. In the screenshot you can see that it triggers at 100mV and later it goes up to around 440mV. With my resistor of 30mOhms this will give 3.3A at trigger point and later (440mV / 30mOhms) 15.0A!
So I think with this huge current the Digi40 is overburdened (max. current of Digi40 is 5.0A).

I did the same test with my new power lab (Manson SSP-8160). I set the voltage limit to 4.0V and the current limit to 2.0A.
I got similar voltage (over 400mV) but for some reason the Manson could handle the huge current even if it was limited to 2.0A.
Why my Manson could handle over 10A (even limited to 2.0A) and my Digi40 cannot?

What I also wonder is why does the S110 take such huge current peaks before it is switched on just after connecting the power source?

BTW:
Long time ago during my education I have learned to measure fast changes in current / voltage using an oscilloscope. A digital multimeter is much too sluggish to measure fast transitions.
And to use a shunt resistor is a common way to get the current by the voltage measured using an oscilloscope.
« Last Edit: 04 / May / 2015, 14:54:05 by mr.burns »
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