Roomba Red Charging Circuit Repair/Troubleshooting

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Postby bitbuster » May 14th, 2007, 12:39 pm

yes
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Postby finfin » May 14th, 2007, 12:40 pm

Thanks, Bitbuster! I'll see if I can locate some today.
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Postby finfin » May 14th, 2007, 3:43 pm

Did someone say you can use a car battery charger to charge a roomba battery? I looked for a rapid charger at iRobot but I couldn't find one.
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Postby vic7767 » May 14th, 2007, 4:55 pm

If your Roomba has a functional charging circuit but your Roomba battery is below 12 volts DC then the charging circuit will not run. If you have an automotive battery charger, it can be used to bring the Roomba battery up to 12 vdc so that it can be placed in the Roomba and continue a normal Roomba charge.

This post has now been proven to be inaccurate. Even if the battery is at 12 volts or a little lower the charging circuit will attempt to charge it. You may not see the charging indication for a few minutes but if your charging system is working eventually you will see the led begin to pulse red.
Last edited by vic7767 on December 5th, 2007, 10:36 pm, edited 1 time in total.
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Need to replace MOSFET

Postby bortek » November 20th, 2007, 4:36 pm

Hi everyone,

I have the same problem with MOSFETs U2 and U4. I was trying to find online shops in Europe that would sell STN3PF06 to Sweden but could not find any.

I would be really grateful if someone could suggest a good place to buy STN3PF06 online.


Regards,
/Boris
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Re: Need to replace MOSFET

Postby Gordon » November 20th, 2007, 9:27 pm

bortek wrote:...I would be really grateful if someone could suggest a good place to buy STN3PF06 online. ...
Boris, have you tried the UK outfit: rswww.com?
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Postby Gordon » November 20th, 2007, 10:03 pm

finfin wrote:Did someone say you can use a car battery charger to charge a roomba battery?
Prior to vic7767's recent post, I don't recall anyone saying its OK to use a car battery charger, but such a statement could exist. However, there is a suggestion to use a car battery to add some charge to a weak Roomba-battery--posted earlier in this thread, I believe.

Fundamentally, either energy source can be made to serve, but you might want to pay attention to a couple things. Things like *surge-current*, and *battery-heating*.

Either of those two energy sources can delivery more current than a Roomba battery normally experiences, so if you directly connect the charging source to the Roomba-battery, I can envision the possibility of opening the 4A-fuse when high surge-current initially flows.

If the initial surge is not that high, there is likelyhood of a continuous high-current going into the battery and generating heat due to the forced chemical reaction--which would not be good for even a healthy battery.

To control charging-current, you must insert some low-value of resistance between the source and battery. Ideally, that resistance would be adjustable. It would be beneficial to also insert an ammeter in series, so you could see what current was being delivered.

Even then, you should not leave the setup unattended.

I looked for a rapid charger at iRobot but I couldn't find one.
Look on eBay. The Rapid Charger is no longer in production.
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Postby vic7767 » November 20th, 2007, 10:43 pm

The statement I made previous in this thread is inaccurate and I will attempt to correct it. In the past it was my impression that if a Roomba battery dropped below 12 volts dc then the Roomba charging system would not attempt to charge it. That is now a myth and totally false. The Roomba charging system may not display any activity when attempting to charge a battery at 12 volts or even below that. You may not see the LED flash (Pulse) for a time. But internal things are happening between the battery and the Roomba software. If the software determines that there is a possibility the battery is capable of receiving a charging current and voltage then the LED begins flashing and the battery is exposed to a charging current and voltage until the software determines the battery is completely charged at which point the LED goes green and a trickle or float voltage and charging current is applied for as long as the battery is in place and the charger connected.

The other statement of using an automotive dc charger to bring the Roomba battery up to 12 volts can be accomplished but I failed to mention that I had only done this using a charger that has a SLOW CHARGE 2 amp setting. The charger and battery must be constantly monitored and the battery should be disconnected after a 30 minute exposure to the charger. Let it rest, test the charge level and repeat no more than twice. If it won't respond to a 2 amp charge it won't charge on a Roomba and probably has a defective cell or two. It would then be time to convert to LI-ion.
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Postby bortek » November 21st, 2007, 2:32 pm

Hi Gordon,

Yes I tried RS and all its local sites. Unfortunately they only deliver locally, that us US RS website deliver to UK only and so on. There is a Swedish rsonline shop but they sell parts only to companies :(

Any other suggestions?


Regards,
/Boris
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Postby Gordon » November 21st, 2007, 4:55 pm

bortek wrote:...Yes I tried RS and... they only deliver ... to UK only and so on. ...Any other suggestions?...
Too bad. I have no other ideas for you except: a) you should re-post your query-post, of the 20th, in the International Robotics Forum. Maybe someone will spot it and give advice, and b) look in the Buy/Sell/Trade Forum for the Roomba-repair 'shops' and ask them if they will ship a replacement main_PWB to you.

Regards;
---Gordon
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Postby OngCL » December 5th, 2007, 10:13 pm

[quote="finfin"]My Roomba (Marvin) is also not charging it's batteries It is a Scheduler that I bought a little over a year ago. The power supply is reading 22.63 VDC but the Roomba battery connections are showing 4.98 and 4.87 VDC with no battery connected. I haven't seen a lot here about voltages but I expected to see more like 7.5 or higher. any thoughts on how I should proceed? Are there any guides on trouble shooting this board? Are you commonly seeing replacement of U4 and U2? I've got a scope I could put on it If someone has so expertise on where to look and what I should see. I keep seeing the mention of a schematic but all I get at the sight is a txt document. Is there really a schematic somewhere?[/quote]
My roomba having problem as above. can anyone advice what should be the voltage on the unit ?
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Postby vic7767 » December 5th, 2007, 10:44 pm

OngCL, you will probably find some additional info in the hacker forum. You could use the advanced search for "Schematic" and you should get Gordon's files.

The voltages you are reporting are consistent with measurements at the charging terminal on the home base. Where are you taking your readings ?
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Postby bortek » December 10th, 2007, 12:28 pm

Hi all,

My charging circuit started to work after replacing U2 and U2 with the native N3PF MOSFETs. Took some time until I found them in Sweden via one of the dealers.

I have 8 of these MOSFETS left if someone is interested.


Meanwhile I got into another trouble :(

My side brush stopped working after I accidentally mixed J18 and J19 connectors on the PCB. I did not note down the colors and thought there were all different, obviously my fault:( As a result J18 became shorted as J19 is a switch.

Does anyone know part could have burned? Must be some transistor or diode but without schematic its quite difficult to know which one.

Any help would be appreciated.

/Boris
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Postby Gordon » December 10th, 2007, 3:24 pm

bortek wrote:...Does anyone know part could have burned? ... without schematic its quite difficult to know which one. ...
Find schematic_8 for Edge-Brush Motor & Driver in this thread; and schematic_10 for Right-Wheel Drop-Switch ckt is attached below.

Inadvertent substitution of a mechanical-switch for the Edge-Brush Motor will have over-stressed its xstr-switch "Q36", and maybe other parts. Q36 is a TO-92 package located on the aft-face at 219 mm to right of LH end of PCB, and down eight mm from upper edge. Let me know if you need coordinates of other parts.

Note: Component-labels prefixed with "f", signify the part is mounted on the forward face of the main_PWB.
Attachments
schematic#10.JPG
Right-Wheel's Drop-Switch Circuit (Discovery Series)
schematic#10.JPG (69.68 KiB) Viewed 7596 times
Last edited by Gordon on September 7th, 2008, 7:22 pm, edited 1 time in total.
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Postby bortek » December 10th, 2007, 4:13 pm

Gordon, thanks for your detailed description and schematics. I'll have a look at ti.

cheers
/Boris
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Postby OngCL » December 13th, 2007, 11:44 am

My roomba is also not charging it's batteries. the power light showed "red" and been flashing for few day. but when pree on power switch, nothing happen. I had measured the power supply jack and is reading 22.63 VDC but the Roomba battery connections (the 3 pin in the battery compartment) are showing 4.98 and 4.87 VDC with no battery connected. Is this voltage indicate the charging circult is good.
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Postby Gordon » December 16th, 2007, 1:26 pm

OngCL wrote:My roomba is also not charging it's batteries. the power light showed "red" and been flashing for few day.
Not good!
... but when pree on power switch, nothing happen.
Not good!
... I had measured the power supply jack and is reading 22.63 VDC
Good!
but the Roomba battery connections (the 3 pin in the battery compartment) are showing 4.98 and 4.87 VDC with no battery connected.
You will have to do a more precise reporting of what points were measured to obtain those voltages. If any one of them happens to be between Batt(+) and Batt(-), your battery may not be usable.
Is this voltage indicate the charging circuit is good.
Can't answer that, because your data are unclear. In addition, most owners will not have electronic test equipment that permits them to make direct measurements on an active charging-controller circuit. I fall in that class, and I expect you do too.

You must then resort to indirect measurements / assessments to determine whether the problem is with your internal controller, the battery, or with the power-supply. That 'indirect' tactic includes:
a) Battery is shown to charge via means separate from the suspect robot.
b) The charged battery is shown to power a load which simulates the load the robot would apply to it, and powers that load for an appreciable fraction of expected running time.
c) Battery's charging power-supply (viz, "APS Fast Charger") is shown to provide nominal charging voltage (which you have done), and supplies nominal charging current to a battery, or to a dummy-load.
d) When measurements and observations of (a) through (c) confirm those accessories are performing nominally, and you put that (known-good) battery into the robot; then connect the (known-good) charging power-supply directly to the robot and AC power it to begin the charging process, IF charging does not complete within a few hours it is fair to say: 'The robot's charging-controller is not working properly'.
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S8050 needed

Postby bortek » March 27th, 2008, 9:47 am

Hi,

I found Q36 to be totally broken after shorting J18 connector. I am now looking for replacement for this S8050 in TO-92 packaging transistor. There several such transistors on the PCB so I though it would be easy to find the new ones on the net. After some searching I actually could not find any shops online that could sell this transistor.

Any idea where I can by it (preferably to Europe) or are there any replacement transistors which are more wide spread.

Many thanks

/Boris
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Re: S8050 needed

Postby Gordon » March 27th, 2008, 2:22 pm

bortek wrote:...I am now looking for replacement for this S8050 ... I actually could not find any shops online that could sell this transistor {to me in Sweden}. ...
DigiKey does not stock them, but Mouser does (only US$0.05, one each!).

I did some googling, found some Frenchmen seeking S8050 alternates, and one of the respondents suggested the ZTX450. It appears to be a 'better' xstr than the S8050, so it would cost you closer to a US-dollar. Perhaps you can source that device in your purchasing area.

If not, start over with the googling searches. Search first for the S8050's data-sheet, then read and note its dc-characteristics. Follow that with a search for "s8050 equivalent". Sort through the chaff, and you may find some European discussion forum that will lead you to an alternate xstr. When you find one, d/l its data-sheet and compare dc-characteristics to make sure they do not fall below the S8050's.

This S8050 application is that of a very simple dc-switch, so all you have to match, or exceed are its Maximum Ratings, and make sure h_FE3 is not less than the S8050's.
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Postby bortek » March 28th, 2008, 4:30 am

Great suggestion Gordon. I will try to find equivalents.

Regards,
/Boris
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