3pi calibration issue

Hello,
We are now facing for the second time the same calibration issue with the Pololu 3pi robot.
First, let me explain that we have bought two 3pi robots for our project.
If one of them was fully functional, it was impossible to correctly calibrate the second, because its sensors values remained to 0 after the calibration procedure. So, we sent back the 3pi to the reseller for an exchange, and the new 3pi worked properly only for 3 weeks. Then, the same issue happened again without any other explanation.
Can you please provide us support

Best Regards

Hello.

I am sorry you are having problems with your 3pi. It is unclear what might be causing your issue. Could you tell me more about the problematic 3pi? What are you having the robot do? Do you have one of our example programs loaded onto it? Do you have any additional sensors or components connected to the 3pi? What kinds of surfaces are you using the 3pi on? Could you post pictures or a video of the 3pi that shows the sensor values after calibration?

- Jeremy

[quote=“JeremyT”]Hello.

I am sorry you are having problems with your 3pi. It is unclear what might be causing your issue. Could you tell me more about the problematic 3pi? What are you having the robot do? Do you have one of our example programs loaded onto it? Do you have any additional sensors or components connected to the 3pi? What kinds of surfaces are you using the 3pi on? Could you post pictures or a video of the 3pi that shows the sensor values after calibration?

  • Jeremy[/quote]

Thanks you Jeremy for your quick answer.
The loaded program is your example: 3pi-line-follower-pid.
We want our 3pi robot to follow a black line.
After the calibration phase, the sensors value remains to 0 and our 3pi robots are used on a simple wood table with black tape for line following.
We do not use any additional sensors or any other connected components.
The 3pi worked fine for 3 weeks and the 3pi is not detecting anymore the black line.
We have examined the sensors with a magnifying glass, and none of them look damaged, disconnected or broken.
Furthermore, we also have tested them (the sensors) with a strong light applied on them with a torsh of an iphone application, and then we noticed response from sensors as bars appear.

If the IR sensors are responding to other IR sources, it sounds like an IR emitter got damaged. The front facing camera on iPhones typically do not have IR filters, so you can use the camera to see if the IR LEDs are turning on. If one or more of the emitters are damaged, I do not expect them to turn on. If you have a multimeter that has a diode test mode, could you try measuring across each IR emitting diode to make sure they each have the same voltage drop? (You can see how the diode is oriented on the top silkscreen on the 3pi.) Could you also post pictures of both sides of the 3pi?

- Jeremy

It seems that the IR emitters of the sensor are dammaged because all the IR LEDs ( 5 in tolal ) are alawys OFF(see pictures enclosed)
For the 3pi dammaged find enclosed pictures of both sides and pictures of the IR LEDS that never turn on.
For an other 3pi (working fine) find enclosed pictures of the IR LEDS that are turning on.

Could you please advise us?
Should we change the 5 IR Leds? If yes please give us the reference of the component?
Or investigate on other component?
3pi dammaged.pdf (410 KB)

The IR LEDs are connected in series, so if one of them is damaged, it will prevent all of them from turning on. As I mentioned in my previous post, you should try measuring across each IR LED to see if they have the same voltage drop to determine which one is damaged.

- Jeremy

The measure of drop voltage is given below:
U4: 1.037V
U5: 1.036V
U6: Over limit
U7:1.037V
U8:1.117V

U6 and U8 do not have the same voltage drop than others.

Could you please advise us?
Should we change U6 and U8?
Can you confirm us that QRE1113GR is the reference of the component?
Can you provide us this components?

Thanks for taking those measurements. It looks like U6 is probably damaged. The difference in voltage you are seeing for U8 might be variance between the units, so I would replace U6 first and see if that fixes the issue before proceeding to replace U8. The QRE1113GR is a suitable replacement for the IR sensors on the 3pi. If you send us an email at support@pololu.com with your order information, we can look into getting you replacement sensors.

By the way, it is possible that U6 was damaged from bumping into something, especially since it is the middle sensor, so you might try taking extra precautions against that in the future.

- Jeremy