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Topic: New YwRobot MB102 power module overheats (Read 22587 times) previous topic - next topic

cartoonist

I had a bad experience with this YwRobot MB102 power module too.
I accidentally shorted the 5V output for a few minutes and then the regulator got so hot that the top of the AMS1117 blew off with a little bit of white smoke and a lot of bad smell.
According to the datasheet of the AMS1117 this could not have happened because the regulator has  temperature protection which should have shut down the 5V output.
So I bought a (couple of) new AMS1117 on Ebay and repaired the MB102.
You do not need a new P.C., you need a new O.S.  Linux is free, safe, easy, fast and reliable.

#16
Jun 30, 2015, 05:51 am Last Edit: Jun 30, 2015, 05:51 am by electronicsguy
To clarify mis-conceptions: The USB jack is reversible - it works as input and output. Plus the female port makes sense, according to USB specs. If you want to power it thru USB, and you don't have a USB male-male cable, but a (more commonly used) USB A-type male to micro-usb male, use an adapter like this:

USB to micro-usb adapter

LordKaos

Hi people, beware of the versions of this board..as I see in the pics, it's exactly the same as MB V2 (code: 545043) but in the V2 the pdf datasheet mention that the USB is output, not input. "USB connector is for powering external device. Do not attempt to use it to power the MB-V2""

Which has logic having in mind that the regulator can't operate with at least 1.5 volts more that the regulation needed.

If it needs at least 6.5 volts, it can't never operate using the USB port with 5V as input.

I made a test a few minutes ago with 7.5v input, and the USB gives 5v.
The +V of the USB connector is directly the 5V output of the board, NOT the same as the DC IN.
Pins +5V and +V in USB are connected (tested with the multimeter), not the same with the DC IN.

Check it with a multimeter before apply DC to the USB port.

Here I attach the datasheet of the board.

Greetings!

KAOS

To clarify mis-conceptions: The USB jack is reversible - it works as input and output. Plus the female port makes sense, according to USB specs. If you want to power it thru USB, and you don't have a USB male-male cable, but a (more commonly used) USB A-type male to micro-usb male, use an adapter like this:

USB to micro-usb adapter


completo


JErbes

Regarding the overheating AMS1117 chips, it could possibly be due to the properties of unregulated 9V power supplies. I grabbed a random 9V 500mA unregulated supply out of my junk box and got the following measurements under load.

Open circuit 14.21 VDC; 13.7V @ 9mA; 13.2V @ 32mA; 12.3V @ 110mA; 11.3V @ 230mA; 10.35V @ 350mA; 9.00V @ 530mA.

A 9V 500mA unregulated supply is just that. It will give 9V with a 500mA load.

The absolute maximum input voltage for a genuine Advanced Monolithic Systems AMS1117 is 15V. The Chinese version of the 1117 may not be that generous.

The AMS1117 also seems to be happiest when V-in minus V-out is just above 1.5V.
The issue here is the maximum power dissipation capacity of the surface mount chip which is only 1.2W. Power dissipation is determined by the input/output differential and the output current.

In other words if you have 14 Volts going in and 5 volts going out, 1.2 watts divided by the 9 volt differential equals a maximum current of 133 mA before overheating.

However, if you have 7 volts going in and 5 out, 1.2 watts works out to a maximum current of 600 mA.

My advice is to use a small regulated supply of 12V or lower.

The attached graph (if it shows up) shows the digital voltage and current measurements I got on the unregulated supply.

chupo_cro

#20
Oct 20, 2017, 05:30 am Last Edit: Oct 20, 2017, 05:35 am by chupo_cro
PLEASE note, that the USB connector is connected in parallel with the DC barrel jack
Of course it is not. The USB is connected to 5V output of the regulator and it can be used as both input and output. When USB is used as input then input voltage should be 5V and barrel connector should be disconnected not to power the 5V regulator. Here is another schematics where the connection is more clear.
Chupo_cro

Zapro

Of course it is not. The USB is connected to 5V output of the regulator and it can be used as both input and output. When USB is used as input then input voltage should be 5V and barrel connector should be disconnected not to power the 5V regulator. Here is another schematics where the connection is more clear.
Well the one i had, it was in parallel. The switch didn't disconnect the USB-plug. When i put in 9V in the DC-jack it had 9V in the USB-plug.


chupo_cro

Well the one i had, it was in parallel. The switch didn't disconnect the USB-plug. When i put in 9V in the DC-jack it had 9V in the USB-plug.
Strange. It probably was some badly designed model. On the other hand, I might have such (bad) modules too :-) I didn't check all of them and I order a few now and then from different sources. I burnt one of them just a few days ago, 5V regulator didn't survive accidentally shorted output although it lasted just for a moment. But that wasn't a surprise because I used 12V input.

Regards
Chupo_cro

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