Relay amperage for side car

What relay amperage is needed for the side car?

20 amp, as stated in the electrical hookup rules for the digital sidecar.

We have our digital sidecar connected per instructions. We’re still having trouble with relays. We’re trying to drive a servo, but it’s not moving. We have a button set up to toggle the servo between 0 degrees to 90 degrees. We are printing the value we are putting in to servo.setAngle and also the value getting returned by servo.getAngle(). We can see that on a button push, we are setting the angle to 0 and it returns a small value close to zero. On the next push, we are sending 90 degrees and it returns a number close to 90. Next it’s back to 0 etc. Unfortunately, the servo is not moving.

I checked the voltage between PWR and Ground terminals on a digital IO channel and got 2.5 volts. When I check the voltage bewteen PWR and Ground on a relay channel, it reads 0.0.

I’m stumped as to how the servo can be sending back approximately the right value without actually moving. Also, what should I expect to read with a volt meter on the relay channels?

Any insight is greatly appreciated.

Do you have a jumper set to provide power on the center pin of the PWM cable?

Did you put the jumper in next to the PWM port on the sidecar?

EDIT: Ether beat me to it.

The pins labeled (-) aren’t really “ground”, but I’ll call them that here.

The voltage between the power and ground pins on a Digital I/O port should be 5 volts. If you’re reading 2.5, you probably don’t have the Digital Sidecar powered properly. Are all three of its power LEDs lit? Does the large amber Robot Signal Light blink with the expected pattern? Please describe exactly how the Digital Sidecar is connected to power, so we can help you verify that it really is according to the insstructions.

There is no power on the relay pins on the Digital Sidecar. There are two signal pins and one “ground” pin. Unless a relay is being energized, you won’t find any voltage present.

Unless you install a servo power jumper on a PWM port, you won’t read any voltage there either. With the power jumper in place, you should see 6 volts.

The servo itself doesn’t report its position. When you use the getAngle function, what you get is a scaled version of the position the software is telling the servo to go to.