front and rear bumper investigation

as I’ve previously found out the front and rear bumpers are just resistor ladders, the resistance changes depending upon where the bumper is pressed.
The front bumper resistance changes from left 80 Ohms to right 120 Ohms.
The rear bumper resistance changes from left 2 Ohms to right 3 Ohms

4 thoughts on “front and rear bumper investigation”

  1. Hi, I have an RL2000 and I’m also doing a brain transplant. I have all motors working, and the odometer (tachometer). I’m trying to read the values from the bumpers. When I connect the white wire to 5V and the black wire to A0, and do an analogRead(A0) for this, I get 1023 when I press the bumper. Otherwise, it fluctuates widely between 0 and 1000. I also tried using the 3.3V power and had the same experience, only with smaller values (678 on press).

    Is this the correct way to hook up the bumper sensor?

    1. After I put a 10k resistor between GND and (A0, white bumper sensor cable), with black bumper cable connected to 5V, I’m getting much clearer results. I have now consistently readings of 0s and maybe sometimes up to 3, and as soon as I press the bumper I get a clear 1023.

      However, I’m not seeing the resistor ladder results that you mention. How did you hook up the arduino to get that?

  2. I get the same result from both the left and right pairs of white and black cable for the front bumper. Both output 1023 on the entirety of the front bumper.

    The rear bumper is completely different. With the same setup, I get a low of 1020-1021 and a high (bumper pressed) of 1023. There is a clear difference, only it is tiny. I’m not sure what to make of it yet.

    1. Hi Lars, if you look at the post you’ll see that the resistance changes between 80-120 Ohms and the rear between 2 and 3 Ohms, therefore for the resistor ladder to give meaningful results you’ll need to use resistors of an equivalent value, i.e. if you use a 100Ohm resistor for the front then you should get readings between 465 and 570 see

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.