I have a motor shield connected to a Uno. I am using it to operate a model rail layout. The issue is that the locos don't start reliably, even on freshly-cleaned track. I am supplying the board at 12 V DC, and using PWM settings up to about 10% - I figured this would be best for overcoming dirty track etc by applying the full 12 V to the track. But I find that, with the loco not on the track, the shield is only supplying about 0.3 V to the track, with the PWM ratio at about 10 %. However, when the loco is on the track and moving, the voltage is about 2.4 V. Why is the voltage so low when there is no load on the driver, and RISES when there is load?
Thanks. I forgot that it was out of 255. My idea of using a high input voltage with a low duty cycle seems to work better than a lower voltage and higher duty cycle. But I still don't understand why the output voltage rises when there is a load. Shouldn't it be regulated to maintain a constant voltage regardless of load, up to the maximum current it can supply?
How have you determined that the voltage is 0.3v ? You are suing PWM to drive what i suspect is a mosfet, so the voltage you measure may not be the power that is actually suplied. The loco may have a capacitor on board which will be charged up to a minimum level, which is what you measure.
Can you post a link to the motor shield you are using ?
If you want to start moving a locomotive, i would want to overcome the stall first, so for about .5 to 2 secs i would just provide full power and start regulating thereafter.
Thanks for your replies. They have given me food for further thought. The measured voltages might be invalid because of how the digital multimeter is responding to the square wave output of the motor shield. I'll do some more experimenting with the idea of a "starting impulse".
Can you please post a copy of your circuit, a picture of a hand drawn circuit in jpg, png?
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.
Are your motors 3 pole or 5 pole?
3 pole are usually the harder to begin to turn.
Do the motors start reliably when off the track?
