Testing Roomba 530 main PCB on its own

The very latest news and updates for the iRobot Roomba robotic vacuum, the Scooba Robotic Washer and the Dirt Dog workshop sweeper. All discussion and troubleshooting questions go here.

Testing Roomba 530 main PCB on its own

Postby AdrianM » May 17th, 2017, 4:56 pm

Hi all, sadly my first post here is to seek help repairing my 530. I while ago I did a small mod involving an electric imp WiFi module which gave me the ability to send commands over http. Recently I got an Amazon Echo and started creating a skill for voice control.

Unfortunately, while doing some current checks with roomba powered-up and the case open, I accidentally touched a meter probe bearing Battery +ve onto the main PCB somewhere around the left motor driver. Immediately the vaccum motor started to run and nothing else worked, but I can't see any direct way I damaged the vacuum driver.

I'm pretty sure I actually blew U4 74HC02 by touching 14V to pin 13 via the common end of R193&194. All the transistors in the H-bridge around here check out OK (left motor). I'm guessing an overall issue with all the H-bridge drives because If I current-limit apply power, it draws several hundreds of mA and all power transistors begin to warm.

What I then tried was just power the 5V side bypassing the 5V buck. The 5V system draws only 10mA so I was hoping the CPU was just in sleep mode - but it doesn't wake when asserting DD over the SCI. I was hoping that it might allow me to test the PCB disconnected from all the peripherals but it's as though it won't come out of sleep mode unless some criteria are met. Either that or the ARM chip is dead (it is run off 5V is it not?). :o

Do we know if it's expected that SCI can wake and interrogate an otherwise isolated main PCB (i.e. no sensors or motors plugged-in)?
AdrianM
 
Posts: 22
Joined: May 17th, 2017, 4:27 pm

Re: Testing Roomba 530 main PCB on its own

Postby a1robotrepair » May 17th, 2017, 6:41 pm

Yes to:
Do we know if it's expected that SCI can wake and interrogate an otherwise isolated main PCB (i.e. no sensors or motors plugged-in)?

You should try removing All modules, front bumper and chassis cover. Does the clean led light when pressed? And, Does it charge a battery...5V is Ok.
R3 section of this post will help the electronicly minded.http://www.robotreviews.com/chat/viewtopic.php?f=4&t=19533
Roses are red Violets are blue Poems are hard Flowers and Chocolate
http://www.daycounter.com/Calculators/
a1robotrepair
Robot Master
 
Posts: 752
Joined: October 14th, 2013, 8:40 am

Re: Testing Roomba 530 main PCB on its own

Postby vic7767 » May 17th, 2017, 6:51 pm

Yes, the circuit board can operate without any peripheral components at all. Normally I will connect just the speaker so that some errors can be reported as well as the standard beep tones. The SCI should wake when DD goes low.
Roomba and Neato Mods, come visit: http://www.vic7767.com/

http://www.Robot-Doc.com/
User avatar
vic7767
Robot Master
 
Posts: 14284
Joined: January 14th, 2006, 8:31 pm
Location: Haughton Louisiana - USA

Re: Testing Roomba 530 main PCB on its own

Postby AdrianM » May 18th, 2017, 6:26 am

OK many thanks. At last I've got some signs of life out of the MCU now. The 5V bypass I implemented for testing was referenced to battery 0V but this seems to sit around a volt or so below what is often labelled SYS_RTN.

When I connected 0V, 5V directly across C28 (SMPS O/P filter cap.) the system sprang to life - at least flashes errors!

Feeding a battery supply to the anode of D47 bypasses all the other circuits connected to battery and powers the SMPS alone. This seems to point to a failure in this area as only 3 or so volts appear across C28. Investigating this next.

But it leads me to anouther question - I've been looking at the schematics to see where there's a connection between battery ground and SYS_RTN because to me it looks like a diode drop but the schematics show SYS_RET as being at the end of the battery current sense resistors so there should ony be 0.05R between them. My meter says its around 2K on the resistance range and 0.5V on the diode drop range between battery -ve and SYS_RET (0V pins of all 5V IC's). Do we know why this might be?
AdrianM
 
Posts: 22
Joined: May 17th, 2017, 4:27 pm

Re: Testing Roomba 530 main PCB on its own

Postby AdrianM » May 18th, 2017, 7:36 am

...I'm wondering if this apparent loss of connectivity might be due to a hidden blown track between the SYS_RET ground and the battery ground. My MC34064 SMPS chip GND on pin 4, and C280 input capacitor -ve do not have direct continuity with Q15 emitter or LC filter (and the rest of the 5V powered IC's) as shown in the SMPS schematic.
AdrianM
 
Posts: 22
Joined: May 17th, 2017, 4:27 pm

Re: Testing Roomba 530 main PCB on its own

Postby a1robotrepair » May 18th, 2017, 8:25 am

Measure directly across R257//R235 SysRtn 0.05ohm. Then check to GND solder joints...battery spring connector. 2K? That's a lot of heat to change their R. It will take a lot of soft solder and flux to remove SysRtn Rs. Diode checker should be near 0V. At 2K one could // two 0.1Rs.
If the solder joint is broken there, SysRtn + to GND or the multitude of SysRtn connections to SysRtn + the PCA is probably toast. You should be able to find a 530, 540 or 630 PCA for $40 or so.
Check charging thread in above post.
Roses are red Violets are blue Poems are hard Flowers and Chocolate
http://www.daycounter.com/Calculators/
a1robotrepair
Robot Master
 
Posts: 752
Joined: October 14th, 2013, 8:40 am

Re: Testing Roomba 530 main PCB on its own

Postby AdrianM » May 18th, 2017, 9:30 am

Sorry a1robotrepair, I didn't do a very good job explaining my findings. I hope this picture helps:

irobot-roomba-530.jpg

The continuity between the battery -ve, 0.1R's and input to SMPS are all good. Continuity also exists to all the H-bridge Power transistor grounds etc.

Assuming the above circuit is called SYS_RET, it does not have low-impedance continuity to the 0V return connection for the 5V supply rail. I see this also labelled as SYS_RET in various schematics but it isn't on my board. Marked in blue in the above image is the 0V end of the SMPS output capacitor C287. This has continuity to everything on the 5V supply bus - but not the input capacitor C280 which is kind of odd and may explain why the SMPS is not putting out a stable 5V.

If these two circuits are indeed meant to be at the same potential, I see no harm in linking them with a wire. Out of interest, is this a multilayer PCB?
AdrianM
 
Posts: 22
Joined: May 17th, 2017, 4:27 pm

Re: Testing Roomba 530 main PCB on its own

Postby a1robotrepair » May 18th, 2017, 11:32 am

Both caps right solder joints are SysRtn + connections, viewed per your pic. Yes, multilayer, SysRtn in one of the center layers.
SysRtn + is where you have your arrow on the 2 0.1Rs.
Roses are red Violets are blue Poems are hard Flowers and Chocolate
http://www.daycounter.com/Calculators/
a1robotrepair
Robot Master
 
Posts: 752
Joined: October 14th, 2013, 8:40 am

Re: Testing Roomba 530 main PCB on its own

Postby AdrianM » May 18th, 2017, 12:14 pm

a1robotrepair wrote:Both caps right solder joints are SysRtn + connections, viewed per your pic.

Well spotted regarding to my mistake pointing to the + terminal on C287 :D
a1robotrepair wrote:SysRtn + is where you have your arrow on the 2 0.1Rs.

Just to clarify, why did you follow SysRtn by a "+" ? There's just the one SYS_RTN right?

Anyhow, I joined the grounds but the 5V was still wavering around. I lost patience trying to debug the outboard FET driver so I desoldered all the parts relating to the MC34063 (such a quaint old part!) and replaced everything with a 3Amp 5V buck module that has a quiescent current of a few 10's of uA instead of the 5-10mA in the original.

Now the SCI is up and running cool so on to BiT!
AdrianM
 
Posts: 22
Joined: May 17th, 2017, 4:27 pm

Re: Testing Roomba 530 main PCB on its own

Postby a1robotrepair » May 18th, 2017, 12:31 pm

Well played Maestro. Yes, 1 sysrtn. The side not connected to GND is amplified and signal sent to MCU as a V for current calculation. The side I have listed as (+) is positive V when running and negative V when charging. SCI output interpreted opposite readout of SysRtn V drop.
Roses are red Violets are blue Poems are hard Flowers and Chocolate
http://www.daycounter.com/Calculators/
a1robotrepair
Robot Master
 
Posts: 752
Joined: October 14th, 2013, 8:40 am

Re: Testing Roomba 530 main PCB on its own

Postby AdrianM » May 18th, 2017, 4:12 pm

All checked out now and back on the carpet. Thanks again for the infos vic7767 & a1robotrepair. Roomba is getting smarter and stronger by the year. I hope to get back here with an update on the Alexa voice control. I keep meaning to write-up the mods I've done already - 4200mAH LIFEPO4 battery conversion and WiFi being the most useful so far.

BTW, in sleep mode the current now drops to under 3 mA on a full battery using a more up-to-date SMPS for the 5V rail. Well pleased with that.
AdrianM
 
Posts: 22
Joined: May 17th, 2017, 4:27 pm

Re: Testing Roomba 530 main PCB on its own

Postby vic7767 » May 18th, 2017, 5:23 pm

AdrianM wrote:BTW, in sleep mode the current now drops to under 3 mA on a full battery using a more up-to-date SMPS for the 5V rail


Pictures, part number and procedures would be nice to share here on rr.
Roomba and Neato Mods, come visit: http://www.vic7767.com/

http://www.Robot-Doc.com/
User avatar
vic7767
Robot Master
 
Posts: 14284
Joined: January 14th, 2006, 8:31 pm
Location: Haughton Louisiana - USA

Re: Testing Roomba 530 main PCB on its own

Postby AdrianM » May 19th, 2017, 5:04 am

vic7767 wrote:
AdrianM wrote:BTW, in sleep mode the current now drops to under 3 mA on a full battery using a more up-to-date SMPS for the 5V rail


Pictures, part number and procedures would be nice to share here on rr.


OK, see here :D
AdrianM
 
Posts: 22
Joined: May 17th, 2017, 4:27 pm

Re: Testing Roomba 530 main PCB on its own

Postby vic7767 » May 19th, 2017, 9:31 am

Thanks a bunch. This is a great mod and lots of detail. I'm sure some brave souls will attempt this on their 5XX Roombas. :cheers:
Roomba and Neato Mods, come visit: http://www.vic7767.com/

http://www.Robot-Doc.com/
User avatar
vic7767
Robot Master
 
Posts: 14284
Joined: January 14th, 2006, 8:31 pm
Location: Haughton Louisiana - USA

Re: Testing Roomba 530 main PCB on its own

Postby AdrianM » May 19th, 2017, 12:54 pm

I'm not sure if some damage remains from my 'little accident'. Everything works OK but where the charge state 4 - (waiting) current used to be reported over SCI as around 150mA it's now around 220mA. I could do with knowing a "normal" range before I strip it down and start testing each peripheral again..?
AdrianM
 
Posts: 22
Joined: May 17th, 2017, 4:27 pm

Re: Testing Roomba 530 main PCB on its own

Postby a1robotrepair » May 19th, 2017, 7:53 pm

Battery baseline current? Min -300, Max -13 mA. Probably not a problem but something blew your SMPS circuit.
Roses are red Violets are blue Poems are hard Flowers and Chocolate
http://www.daycounter.com/Calculators/
a1robotrepair
Robot Master
 
Posts: 752
Joined: October 14th, 2013, 8:40 am

Re: Testing Roomba 530 main PCB on its own

Postby AdrianM » May 20th, 2017, 7:33 am

Well, having checked, all current is now being over-reported by a factor of 1.32
R235||R257 are not out by as much as that so I'm checking around U8.
U8opamp.png

I'm thinking that Q19 Is turned on to zero calibrate the current reading - do we know any more about this?

Of course now I've run down the battery, putting it on the Roomba charger gives ERROR 2 (overcurrent) even though it's not so I'm having to charge with a benchtop CC/CV PSU set to around 1A.
AdrianM
 
Posts: 22
Joined: May 17th, 2017, 4:27 pm

Re: Testing Roomba 530 main PCB on its own

Postby AdrianM » May 20th, 2017, 11:03 am

Correction: I was wrong to say the sense resistors were out of spec! When I took the trouble to insert a DVM in series with the battery I found I wasn't actually feeding it 1Amp like I thought. So when I did measure the volt-drop correctly, the resistors were close to to 70milliohms hence the high current readings. I guess the accidental short upset them. While I do have a polyfuse inline with the battery pack the actual incident was over in a split second before it opened.

For now I've strapped a couple of 0.33R in parallel to arrive at 0.049R and SCI now reports 1005ma while my DVM says 1000ma. I may leave it this way - knowing the first thing to suspect if current goes haywire again :oops:
AdrianM
 
Posts: 22
Joined: May 17th, 2017, 4:27 pm

Re: Testing Roomba 530 main PCB on its own

Postby a1robotrepair » May 20th, 2017, 2:25 pm

Q19 is more than likely used for the baseline current calculation. Turning it on will force a known V across the series 90.9, 0.05 and 90.9 ohm Rs and setting up a known series current for MCU. There is a weak joint in that circuit. One can usually find it using continuity checks.
Roses are red Violets are blue Poems are hard Flowers and Chocolate
http://www.daycounter.com/Calculators/
a1robotrepair
Robot Master
 
Posts: 752
Joined: October 14th, 2013, 8:40 am


Return to iRobot Roomba and Scooba Chat

Who is online

Users browsing this forum: a1robotrepair, jsms, TechGuy and 403 guests