R8/9 Motor Drive - please measure the voltage output

[marknorton]

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OK, the BQ2010 is a slightly ageing battery "gas gauge" and is used to determine the charge state of the batteries; it monitors battery current by measuing the voltage across the two paralled R100 resistors and the battery voltage on pin 11 via a resistive divider made up of the 9103 and 1303 resistors. The ratio 91/13 is 7 which is 1 less than the number of cells and is used to determine what voltage from the battery pack counts as empty, 0.95v per cell in this case.

 

[ BTW: pin numbers start at 1 and move anti-clockwise so that pin 9 is opposite pin 8]

 

The components in the middle are to do with programming the voltage levels at which the 3 LEDs activate and the star earth is there to prevent the high current flowing from the battery upsetting the chip's ground reference. The blue wire connects the thermistor to the charger to prevent over-temperature charging, The yellow wire tells the camera when the battery pack is empty and you should think of the yellow wire as an output, not an input.

 

It's an open drain output which goes high impedance when the battery is empty, so one way to monitor that is to connect a 10k resistor between the yellow and red wires and monitor the voltage on the yellow pin. It should be close to 0 when the battery pack is charged, close to the red pin voltage (measured relative to the star earth) when it is empty.

 

Try this - disconnect the yellow wire from the circuit board. If you leave the lead disconnected, that wire is now "high impedance" and I expect if you connect it to the motor drive, you will see some voltage on the yellow wire due to an internal pull-up in the motor drive. I expect the motor drive will then not run because it thinks it has a flat battery.

 

Then, try connecting the loose end of the yellow wire to ground - which might have been similar to what you did with your diode if you connected the banded end to the black wire. The motor drive should then run.

[marknorton]

Also, measure the voltage on pin 16 of the chip - on the opposite side of the dot - should be 3 - 6.5v, depending on the state of charge. The transistor is a simple voltage regulator designed to provide the chip with a more-or-less constant working voltage for it's own operation; you should find the voltage on pin 15 similar. Don't short the pins together!

[rick_dykstra]

Hi Mark. Thanks for this.

 

As you suggested, when the yellow wire is connected to black, the motor runs. When this connection is removed, the motor doesn't run. Note that it is over-running too. I'm wondering if the relay(s) is/are sticking, or if the capacitor is not doing it's job.

 

Voltage at pin 16 is 5.3v. At pin 15 it's 3.6v.

[marknorton]

You can rig up your own "battery OK" light, by using an LED and 1k resistor in series. Connect the anode of the LED to battery pack pin 2 (red), the cathode to one end of the resistor and the other end to battery pack pin 3. The LED should come on if the battery pack is OK, stay off if it is not.

 

Since the batteries are of a different type to those originally used, I'm not sure the LED check lights will ever work properly. Pins 2 to 7 are used to tell the chip about the battery pack; Pins 2 and 4 are pulled high by the 1003 resistors, Pins 3, 5, 6, 7 are left floating. This sets the chip's knowledge of the battery type and capacity and although it learns (because it is permanenty connected to the battery pack), it may or may not be able to accomodate a wildly different battery spec.

 

I'm surprised at the voltage on Pin 15, it's a bit low.

 

As for the motor drive overrun, a standard technique when you want to stop the motor is to short both pins of the motor together. This causes - in a typical DC motor - an instant braking effect and the same technique is used in the M-winder. In the motor drive, I expect this is done by the relay and if the relay is sticking, the motor will run on, though I'm surprised the motor drive is not coming up against a mechanical stop in the camera.

[rick_dykstra]

I can see that different cells could confuse the chip - 1500mAh originals vs the 2000mAh replacements. The LEDs operated correctly though. I checked them often during a number of use cycles, and then discharging and recharging. All seemed well, just with the times extended.

 

I had a good look at the motor and gear box and saw nothing I thought was a mechanical brake. There is a castellated disc that spins through a groove in a sensor which is connected to the circuit - a revolution counter I think.

 

I'm thinking that replacing the relays would be a good idea. But what about that capacitor? What would be caused by it failing? Could it be the source of the motor running problems? Why am I not seeing 10v when measuring between red and yellow? If I bypass the capacitor I get the 10v and a motor that motors.

 

Should I try a new 0.1uf capacitor there, and what sort should I get?

 

Thanks for your help on this. I'm wondering what you do for a living. An electronic engineering consultant to Leica AG perhaps. And the Stig on your days off.

[marknorton]

I don't believe the capacitor is faulty for one second and, even if it were, it wouldn't cause much of a problem. It's there to add a bit of noise immunity to the line by implementing a low pass filter (together with the pull up in the motor drive).

 

There won't be a mechanical brake - that's provided by the DC motor - if such a motor is running and the power is removed, it will continue to run due to mechanical inertia and act instead as a generator. By shorting the two contacts together, current flows in such a way as to counteract the motor rotation and it rapidly comes to a halt.

 

If you can trace the motor wires back to the relay, that might help explain it. Keep in mind the relay has two connections for the coil, and two sets of change over contacts - each set consisting of a common, a normally open and normally closed contact when the relay is unenergised.

 

The castellated disc will be to detect motion and prevent the drive stalling and burning out the motor - look to see if there's any irregularity in the disc which might be used to detect not just motion but the end of the winding cycle as well. Look too for some sort of optical switch with a moving vane interrupting it at the end of the winding stroke, as on the M8.

 

The power to the motor is from the red and black wires via the relay in all probability and that's what you should be measuring. The yellow wire is simply there to provide a logic "Power Good, Power Bad" signal; if it's bad, the motor will not run, as you've discovered by disconnecting the wire. If it's good, it's equivalent to grounding the yellow wire and the motor runs.

 

As for replacing the relay, keeping in mind its likely role in braking the motor, I think that might be useful but 9v is not a common coil voltage and the direct Panasonic relay might be difficult to source. Try measuring the voltage across the coil when it is activated. What's the coil resistance?

[rick_dykstra]

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I've found a couple of sources for the relays. Overseas for the Panasonic DS2Y-S-DC9V relay, and here in Oz for an alternative.

 

But what can be done about the battery pack? It only makes the motor drive function (albeit imperfectly) when the yellow wire bypasses the capacitor.

[marknorton]

You're not bypassing the capacitor, you are emulating the part of the chip which tells the camera whether the battery is flat.

 

Fine yourself a 12v 5w light bulb to act as a dummy load connected to the red and black contacts; then find yourself the LED and resistor to act as battery good indicator as I described and just work to the get the chip conditioned to the battery by going through a few charge/discharge cycles.

[rick_dykstra]

You're not bypassing the capacitor, you are emulating the part of the chip which tells the camera whether the battery is flat.

 

Yup, I'm with you.

 

To paraphrase - while the battery cells might have sufficient charge to make the motor drive work, if the bq2010 chip in the battery pack is out whack, it will tell the camera there isn't enough charge. The shutter buttons and exposure meter will work, but not the drive. Putting the battery through a series of discharge/charge cycles will 'condition' the chip to the charging capacity of the cells, provided they are in good condition themselves.

 

Please re-word that if I haven't got it right enough. I'm hoping this thread can be of help to others when they find it.

 

Battery, off the charger with you!

[marknorton]

I don't know enough about the R8/9 but doesn't the camera have its own battery for running the camera electronics or does everything run off the motor drive battery?

 

Rick, a consistent mistake you are making is measuring the voltage between 2 and 3 - you should only measure voltages relative to ground (4) in which case 2 should be 10 - 11v, 1 should be 0 and 3 should be 0. It makes no sense at all to measure the voltage between pins 2 and 3 and even less sense to try to interpret anything from what you find. Pin 3 is what is called an open drain connection and there should be no voltage there when measured relative to ground.

 

You can think of 3 as being a switch connected to ground - open when the battery is flat, closed when it is charged - all assuming you haven't cooked the chip in all this messing about!

[rick_dykstra]

The motor drive battery provides power to both the motor drive and the camera. The motor drive instructions state that once the battery charge is depleted enough the motor will cut out, though the camera shutter and meter will continue to operate. In this case manual winding will be necessary.

 

I will give myself some lines to write.

 

I must not measure voltage between terminals 2 and 3.

I must not measure voltage between terminals 2 and 3.

I must not measure voltage between terminals 2 and 3.

I must not measure voltage between terminals 2 and 3.

 

Hey, that's easy with a computer.

 

The cooking I've been doing has been with the motor drive relays. I've not seen any smoke from the battery circuit yet. I'll do my best to not cook anything from now on. To cook one Leica is unfortunate. To cook two is careless.

[marknorton]

The motor drive instructions state that once the battery charge is depleted enough the motor will cut out, though the camera shutter and meter will continue to operate. In this case manual winding will be necessary.

 

That of course is the purpose of the yellow wire - the chip in the battery pack determines "I'm nearly flat", switches the yellow wire to high impedance which is recognised by the motor drive to disable winding. There is enough power left though to keep the meter and shutter release running.

[rick_dykstra]

Putting my souped up battery through a discharge/charge cycle just took six and a half hours. I tried it in the camera/motor drive. No drive! It does light up all three LEDs though. So something good is happening with the chip.

 

As before, it powered the shutter and meter OK.

 

I've put it back in the charger for another empty/fill cycle. See you in 6+ hours.

[marknorton]

That's some progress - the chip is learning about the battery.

 

When it's fully charged, put it back in the camera and measure the voltage on the yellow wire relative to ground, should be 0.

 

Then, drain the battery and put it back in the camera; the open drain should go high impedance and an internal pull up in the motor drive should put 5 - 9v on the yellow wire (my guess).

[rick_dykstra]

The battery has been through two more cycles. Each discharge is taking longer. The last one was five and a half hours. But no drive.

 

I've been reading various tech data publications about the bq2010 'gas guage' integrated circuit, the one in the R8 battery pack. This pub is the most helpful.

 

http://focus.ti.com/lit/ds/symlink/bq2010.pdf

 

The way my battery is behaving suggests that the chip's end of discharge voltage latch is not resetting, which is keeping pin 12 at high impedance, tricking the camera into thinking the battery is flat - hence no drive. I'm looking into how this can be reset. One way is to give it a 'valid charge', comprising 256 Nominal Available Charge (NAC) counts. The other way is to hook it up to a computer and pump some bits into pin 13 (and I know how to count them now! )

 

So far I've been removing the battery from the charger after each recharge, to try it in the camera. Upon inserting it back in the charger it goes through a quick discharge/charge cycle, before accepting my manual intervention by pressing the discharge button. Next time I will leave it in the charger and with the light on green (trickle charging), press discharge. See what happens.

[rick_dykstra]

That's some progress - the chip is learning about the battery.

 

When it's fully charged, put it back in the camera and measure the voltage on the yellow wire relative to ground, should be 0.

 

Then, drain the battery and put it back in the camera; the open drain should go high impedance and an internal pull up in the motor drive should put 5 - 9v on the yellow wire (my guess).

 

I'll keep these instructions in mind for when I dissect the motor drive again (if necessary). Making such measurements would be tricky with the drive in assembled condition.

[marknorton]

The way my battery is behaving suggests that the chip's end of discharge voltage latch is not resetting

 

You're making wild guesses about something which might have gone wrong with the chip - if you use the LED and resistor as I suggested, you'll know whether it's working - the LED should be on when the battery is charged and go out when the battery pack is flat.

 

If necessary, run a couple of thin wires out of the battery pack so that you can measure the voltage when the battery is installed in the camera.

 

Beginning to get a bit bored of this now...

[rick_dykstra]

I don't think I'd call it a wild guess ...

 

I'm happy try your suggestions. I will admit to finding some of the lexicon hard to follow though. Open drains, and the like. I don't have the right background.

 

Is this right?

 

- With the battery fully charged put it in the camera/motor drive combo with wires running from the battery terminals. Measure the voltage between terminal 3 (which connects to the yellow wire inside the battery pack) and terminal 4 (black wire)?? This should be 0.

 

- then, flatten the battery. I'll use the charger's discharge cycle to do this and wait for the end of discharge first warning signal (flashing of LED no 1). Make the same measurement as above. ??

 

The last discharge/recharge cycle took 8 hours - it's stretching out. As mentioned I went straight from full charge to discharge without removing the pack from the charger. I just tried it in the camera. No drive.

 

All three LEDs in the battery pack are working like champions.

 

I know what you mean about getting bored of this. I'm impressed by your stamina.

[rick_dykstra]

Mark, here are the results of testing terminal voltages in the camera.

 

Battery fully charged.

 

red to black: camera off, 10.79v; camera activated, 10.74v.

 

red to yellow: camera off, 10.68v; camera activated, 10.04v.

 

yellow to black: camera off, 0v; camera activated, 0.71v.

 

What I find interesting is the result for the voltage from red to yellow, or terminal 2 to 3. Out of the camera this is 0v. In the camera it goes up to 10v. This looks like the opposite of what it should do, as per your earlier post, #54. Is this what's stopping the drive from working when it should?

 

I've not tried with the battery at its end of discharge state yet. Will advise.

 

As experienced before, if I connect yellow to black, the drive works, though intermittently (possibly those troublesome relays).

 

I also noticed that in doing these tests I lost LEDs 2 and 3. They'd been working fine after the full charges. Perhaps this is the chip in the battery pack saying its almost flat, when it isn't. That's not a good look for the chip. On the next charge I'll see if I can replicate this effect, to be clear about which action of mine caused it. Based on earlier and similar results, it could be the yellow to black test. Or perhaps the yellow to black contact, which makes the drive work.

 

The pics show how I got these measurements. The red and yellow wires are correct for their respective terminals. I used a blue wire to connect to terminal 4, which has the black wire inside the pack.

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Hallo,

Look here: Interesting Leica gear

[marknorton]

As I've tried to explain, the yellow wire is connected to an open drain connection - you can think of this as being one side of a switch with the other side connected to ground (black). The chip opens the switch when the battery is flat, closes it when the battery is charged, or at least is meant to.

 

So, with the battery in the camera, the camera tests the state of this switch by connecting the yellow wire through a resistor to the positive rail (red). If the switch is open, the yellow wire is effectively connected to the positive rail. If the switch is closed, it drags down the voltage towards 0v.

 

So, with a fully charged battery and the camera on, the voltage is 0.71v, actually a bit higher than I would have expected; if the battery is flat, I'd expect the voltage to be higher - depends on how the camera/motor drive regulates the voltage down, but let's say 6 - 9v. The camera then uses that voltage to determine if the battery is good or bad - effectively, a logic 0 and logic 1.

 

I think you should ignore the red-yellow voltage measurements.

 

[Just seen the diagram Leica sent you - this "capacitor" is actually labelled as RV1, so I don't know what it is - might be to prevent the chip being damaged by a voltage spike on the line - sometimes surface mount components are a little shy revealing their identities].