Hi all,
I've got a MotoMama (which uses a 298) and it struck me that the motor runs very slowly (judging by the whirring noise) compared to when it's hooked up straight to the battery. The voltage on the MM output compared to the battery is low, and I wonder if there are some losses in the 298 or something.
For this testing I took the Uno and its sketch out of the pictureand used a standalone supply to provide 5v to the MM logic, it measures 5v at the MM input; power side of MM is from its own 4x AA pack. There's no PD between the grounds of the logic and power input to the MM, but just for the heck of it I hooked them together on the breadboard just to make sure. The MM motor channel enable is hardwired to 5v, the 2 direction leads are hardwired to 5v and 0v for this test. (The unused channel enable is hardwired to 0v for the test, to make sure it's out of the equation.)
Here's some figures:
Battery pack (4x AA) by itself, connected to nothing: 5.7
Battery pack under load of motor clipped to its wires: 5.2 and motor whizzes merrily
Battery connected to Vin and ground of MM: Motor channel disabled (pulled to ground):
Vin on MM: 5.6
MM Motor output: 0 (as expected, it's disabled)
Battery connected to Vin and ground of MM: Motor channel enabled (pulled to 5v hardwired):
Vin on MM: 5.6 no motor connected
MM Motor output: 5.2 no motor connected
Vin on MM: 5.1 motor connected and running slowly, no nice whizzing
MM motor output: 3.4 motor connected and running slowly, no nice whizzing
So here's my problem... in both cases of the motor running, the battery drops from just under 6 to just over 5, ie direct connect to motor or into the 298. But the voltage on the output from the 298 drops to not much more than 3 and the motor is verrrrry sluggish.
Anyone have any ideas? Am I destined to having a 6v motor effectively running at what sounds like half speed thru the MM and its 298?
(The MM datasheet says the motor side can run at 3v. When I use 3v and a 3v motor, it doesn't work at all. Terry of YourDuino suggests 6v on the motor side as a rule of thumb... my rig is nominally 6 but actually lower. So maybe it does need to be over 6?)
Jim