Motors with an earth

**calumco** · 26th August 2008, 19:04

ive got a problem with my featherweight robot which ive been building, because the 2 drive motors and wheels are each from 2 electric scooters, i didnt know this untill i found out but each motor used to use the scooters chassis as an earth which was fine until i put both motors into a steel chassis and now i cannot operate them at the same time because of the fact that they each end up using the chassis as an earth if i connect one motor to the speed controler it works fine but i cant use both, does anyone have any ideas how to get around this problem? thanks

**neontetra23** · 26th August 2008, 19:15

Use 2 speedos, I think, but you should wait for answers from an expert

**Mouldy** · 26th August 2008, 20:14

have you had the motor apart to see if there are any obvious connection between the case and the brushes for example?

if your not electrically minded.. you could try insulating the motor from the chassis- i.e. mount it on polycarbonate instead of steal

**maddox** · 27th August 2008, 06:09

Sounds like the old days, with wiper motors...

**swanaldo** · 27th August 2008, 10:42

if he mounted the motor to say polycarb then wouldnt you need to use plastic gears or chain to insulate it that way too. not sure if it applies from the armature onwards but a thought.

**swanaldo** · 27th August 2008, 10:43

unless the complete drive unit was seperate from the chassis mounted on say poly. that might work

**woody** · 27th August 2008, 11:57

Any chance of a pic of the motors Calum?

IF there are two wires coming out of the motor and one is attached to the casing...simply detach the wire from the motor casing.

**Mouldy** · 27th August 2008, 16:33

swan- i know what you mean, it would work if he was using belts though, which i think alot of the aussies do with those scooter motors

.. but its still better practise, as woody said to look at the motors carefully.. there is normally a wire bolted or soldered to the case some were. cut it..

Calum.. i had this problem with one of my first robots.. even though i thought i un-earthed the motors.. what speed controllers are you using? I used electronize 15amp CPU controllers and wiper motors.. i found that when the heatsink of the controller touched the chassis it would have similar effects to what you describe. Are the controllers your using insulated from the chassis aswell?

**calumco** · 27th August 2008, 20:41

the speed controller is insulated from the chassis, ive taken 1 motor apart and theres no earthwire connecting to the inside of the case so i guess its from the motor shaft then it goes through the case of the motor -is it called a motor shaft??

ill put a picture of the robot so far as my profile pic so anyone can see the motors and the way they are mounted. and yes the welding isnt great at the minute.....

would using 2 speedcontrollers work? which ben read mentioned?? if not it looks like ill be making the motor brackets out of poly and yes there are 2 wires coming out of each motor.