Comments: RedBot Assembly Guide
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The left bumper signal isn't working for me . When I test the outputs from the pins on the control board ,the pins to for the right bumper give 4.58 v. The pins for the left side give nothing, so no signal is going to the bumper sensor to be interrupted to trigger the reverse.
Double check all wiring (including the wires themselves) and physical connections and if you are still seeing problems email our techsupport team and they should be able to help you out.
Already done. I'll head over to techsupport.
The guide shows only connecting 2 wires to the whisker (bumper) sensors (signal and ground). I hooked my robot up that way, but instead of using the RedBot library to read the sensors, I was using a digitalRead. I got very spurious results. I hooked the two wires to an analog input and found that when the bumper was pressed I got a clean 0V (GND), but when the bumper was not pressed the values were jumping all over the place, which explains why I was having problems.
When I added a 3rd wire to the center post on the sensor (5V) and connected that the 5V on the robot it cleaned things right up. Obviously the sensor doesn't have a positive voltage reference when the 5V wire is not connected. Perhaps the Redbot library functions for those sensors handle those spurious signals (perhaps because they use an interrupt that looks for a falling signal).
As a teacher, I don't want my students depending on libraries right out of the chute; I want them to understand what the sensors are doing, and various approaches to using them (digitalRead, interrupts, etc.) Therefore, my recommendation is to change the instructions and have users connect up all 3 wires to get clean results no matter what code they're using or writing. Can't hurt (but costs you 2 more wires).
If you want to read the sensor without the library, you should use INPUT_PULLUP mode rather than INPUT mode for your digital pin.
This is an extremely important concept which tends to be ignored to the peril of the student. Internal pullup resistors on microcontroller input ports are a super useful feature and should be a basic lesson taught at the same time as other modes. In fact, I usually recommend to my students that they always use INPUT_PULLUP as it rarely hurts and avoids situations like this.
Fantastic guide, and a great low cost platform! Please explore using 6V NiMH or 7.4V Lithium Ion batteries as a alternate energy source.
I've used the 7.4V 2-cell Lithium Ion packs with this. They work pretty well; the only problem is that the lowest speed the robot can manage at 7.4V is a little faster than I'd like.