Roomba 530 - charge err 3 and current sense fail

[LazyRoomba]

Probed around Q23, what I found:

[a1robotrepair]

Rule #1 in troubleshooting complex systems, fix all known problems and 90% of the time the unknown problems go away. Q23 needs its emitter pulled low by the MCU. We don't know the programs IO required for this to happen. One could suspect that U8 A4 could have an effect on pin 30 of the MCU. I would first fix U8 A4 and see where that leads.
R3 U8 A4 is very similar to R2 U3 A1 in Gordon's drawing, very bottom white lines: http://www.robotreviews.com/chat/download/file.php?id=1858&mode=view

[LazyRoomba]

True. It now looks like the MCU is intentionally not turning on Q23 because a parameter isn't right.. I'll try and trace each pin of U8-A4 as far as I can go, and see what's driving the incorrect values. But it seems (So far) the charging circuit could be fine.

I'm getting bad readings on the battery temperature, I did retrace the route to the MCU and everything looks fine, but 5Volts is going to the MCU (Indicating a very low temp). For testing, I'm going to short the thermistor with a resistor for now, to get that issue out of the way. Note, 5 volts was at R318, before U8.

Quick probing tho, suggests going down the route of R299, as that has a resistance of 30K to R279.

[LazyRoomba]

Caused quite a bit of destruction to my donor board to get this, but managed it. Bugger likes to mix in.

Bad news is, I've not started on pin 12. Going to dig further from C113.

Using my schematic for pin 13 and 14, pin 12 maybe the source data for A4, can only be verified once ventured past C113.

Edit:
C113 is connected to pin 13, U8.

[LazyRoomba]

Update to pin 13 / 14

Screenshot_26.png (9.15 KiB) Viewed 2281 times

Progress on pin 12

Note: Transistor markings maybe in the incorrect pin layout.

Edit:

Unable to get a datasheet for Q19.

Top to right measures 0.185 volts.
Right to top measures 0.185 volts.

My donor states:

Top to right measures 0.250 volts.
Right to top measures 0.250 volts.

Multimeter was in diode mode. Got nothing for the left pin.

Q19 was the only component that did not match the donor, following my schematic.

[mfortuna]

I am going to move this to the hacking section.

[a1robotrepair]

Cool beans, thanks Mike

[LazyRoomba]

Checked Q19 on another donor, 0.186 volts. So.. Q19 is normal. I really don't know what's next, Just have to analyse the schematic.

Thanks for moving this thread, starting to move towards reverse engineering the thing.

Edit:
Probed pin 12, has no volts and sends roomba into "Dead battery" mode with the sound. Battery has 16 volts. Need to fix this false battery voltage issue, It's affecting my probings. Issue started when I accidentally shorted Q23 to R299.

[a1robotrepair]

I have the drawings for U8 on paper and will need time to put into Scheme It, later in September.

[LazyRoomba]

Cool, tracing up R299, it's heading towards ground, but might give me an idea on the false battery sensing.

Edit:
U11 might have something, hard to tell tho, as it'll be tracing through the ground.

Edit:
Bingo. Will have a schematic soon.

[a1robotrepair]

I find Gordon's article on U8 invaluable. Here are some valuable excerpts.

U8 A1 & A4 Total System Current
Two OpAmps serve this signal conditioning requirement. One amp, (A4), samples the tiny voltages that develop across the master current shunt resistance, a resistance of only 0.05 ohms, NOM. The second OpAmp (A1) adds a relatively large voltage offset to the non-inverting input of A4 (to prevent A4's OUTput from getting too negative).

In Table-III we see that voltage data in Rows 1 and 5 are identical (to the precision reported) and that is good if the magnitude is correct. We can't know whether "1.24V" is correct simply by looking at tabled values. We must know more about the voltage divider that reduces some unknown bus voltage to an appropriate level. Thus, a little extra work was done to give us confidence in the "1.24" number. I began tracing from U8-3, and quickly located both divider resistors, R209 & R218, nearby to U8 (they are near U8's pins 1, 2, & 3 package corner). I then knew where the supply end of the upper resistor, (R218), was located; so it was just a matter of re-powering the main_PCA and measuring that supply voltage. Voila! It is the +5VREG power-form. Therefore, one fourth of five volts is the nominal input voltage to U8-3(IN(+)). Thus, "1.24 volts" is not bad.

Rows 4 & 8 in that table show us how A4's OUTput changes between battery powered operation and charging mode's high-rate charging period. These are the voltages shown in column-D cells, Rows 4 & 8. We can't learn much by trying to make sense of the values in those two cells. Possibly, the easiest way to sort out whether they are correct is to obtain SCI data from the robot while it is powered by a battery that has an ammeter between it and the Roomba. I did not take time to do that work, so I am limited to commenting on the magnitudes of system currents passing through the shunt and determined by using my DVM to measure dV across the shunt. In the battery-powered On state, actual current was computed as I_batPwr ~= +0.0044 / 0.05 = 0.09 A ( value that, from experience is known to be reasonable); and while PSU-powered and supplying high-rate (I_chrg > 1.25A) charging current the actual current was computed to be: I_hiRate ~= 0.056 / 0.05 = 1.3A. A good value.

The latter calculations basically say the master shunt is OK, and nothing about the (row,col) 4,D, 8,D values. Once again, the SCI connection may be the most satisfying tactic to check those data.

Battery Teeminal Voltage Monitoring
n this table we see that voltage data in Rows 2 and 6 are very much the same, but there was an appropriate increase in voltage after charging mode began. Good! We can't know whether those values are correct simply by looking at tabled values. We must know more about the voltage divider that scales VBAT so the MCU can process a sample. Thus, a little extra work was also done in that regard. Now that I was able to begin tracing from U8-5, both divider resistors, R207 & R208, were quickly found nearby U8 (they are near U8's pin-7 package corner). Easier than that was to divide the U8-5 voltage by a measured VBAT value to learn that about 17.4% of VBAT is tapped for the MCU's sample.

Battery Temperature Tracking
In this table the OUTput of A3 remains the same when Roomba is either battery powered or PSU powered. In this test case the explanation is seen in the Row-7 comment, namely, the 10k variable resistance (representing the battery's thermistor) was not changed from its 10k ohms setting after changing power sources. Row-3's comment points out that temperature sensing is active when battery powered, even though Roomba makes no use of those data. The signal on U8-8 (A3-OUT) dropped to 1.0 volts as the variable resistance was reduced to 2k ohms (representing a very hot battery).

Similarly, after completing the charging-mode measurements, I exited the high-rate charging portion of charging mode by simulating an extremely hot battery--the resistance of 1600 ohms was slowly approached, V_pin8 was reading 0.83 volts, and the MCU+F/W halted high-rate charging. Normally, this would be the start of a cooling period.

To obtain more detail about this thermistor data handling circuit visit this thread.

If you care to translate dummy thermistor resistance into thermistor-temperature visit this thread.

Read the full article here: http://www.robotreviews.com/chat/viewtopic.php?f=1&t=17151

[LazyRoomba]

What I found going up R299, I accidentally stumbled upon A1's pin 3 on U8.

Edit:
Thanks for the info. I've checked the voltage divider on U8. Plugged the PCB into my power supply and it won't boot. Checked each component, Nothing on the end of D13..

Edit:
Replaced D13, still nothing after it. I was able to take new readings from U8 after replacing D13 (No more dead battery)

1 - 1.24
2 - 1.24
3 - 1.24
4 - 7.95
5 - 2.71
6 - 2.71
7 - 2.71
8 - 6.5
9 - 6.5
10 - 6.7
11 - 0.07
12 - 0.09
13 - 0.09
14 - 1.3

Note: A3 will be innaccurate, I only have my bench power supply on, nothing is on the thermistor terminals. Since everything looks good, I'll see what BiT says.

Edit, BiT

factory-test 11 battery-sensors
(battery-voltage-ok?) PASS
(battery-temperature-ok?) FAIL
(baseline-current-ok?) mA -234 min -270 max -220 mV 15391 degrees-C -19 PASS

factory-test 12 left-wheel
(baseline-current-ok?) mA -234 min -270 max -220 mV 15391 degrees-C -19 PASS
(left-drive-current-ok?) mA -3 min -150 max -75 mV 15224 degrees-C -19 FAIL
wait: (left-wheel-stall?)


factory-test 13 right-wheel
(baseline-current-ok?) mA -235 min -270 max -220 mV 15391 degrees-C -19 PASS
(right-drive-current-ok?) mA -137 min -150 max -75 mV 15140 degrees-C -19 PASS
wait: (right-wheel-stall?)

factory-test 16 main-brush
(baseline-current-ok?) mA -234 min -270 max -220 mV 15363 degrees-C -19 PASS
(main-brush-current-ok?) mA 0 min -500 max -200 mV 14166 degrees-C -19 FAIL
(main-brush-current-ok?) mA 1 min -500 max -200 mV 14583 degrees-C -19 FAIL


factory-test 20 int-charger-recovery
not (internal-charger-available?) PASS
wait-true-for-half-second: (internal-charger-available?)
(int-charging-recovery-current-ok?) mA -2 min 250 max 350 mV 15836 degrees-C -19 FAIL


factory-test 21 int-charger-on
wait-true-for-half-second: (internal-charger-available?)
(int-charging-current-ok?) mA 0 min 750 max 1400 mV 15836 degrees-C -19 FAIL


factory-test 22 int-charger-trickle
wait-true-for-half-second: (internal-charger-available?)
(int-charging-trickle-current-ok?) mA 0 min 40 max 70 mV 15836 degrees-C -19 FAIL


factory-test 23 charger-watchdog
wait-true-for-half-second: (internal-charger-available?)
(int-charging-watchdog-current-ok?) mA 8 min -31 max 31 mV 15864 degrees-C -19 PASS

I'll run over the temperature issue tomorrow, thermistor is connected, giving a 4.7K reading. Fets passed means the entire fet driver ciruit must be working, but not been turned on for a charger. Hoping it's the temperature.

Edit:
Put a 10K resistor accross the thermistor terminals, 1M ohm shows on my multimeter. temperature still -189.C