I'm trying to have bi-directional control over two electric screw driver motors. They're 4.8V 1A each. I was able to run it directly or turn it on/off using a TIP120 Darlington Transistor.
However, controlling the motor using the SN754410 bridge barely moved the motor.
I know there are many Motor Driver boards out there, but they are all more than $20. The one for $20 is based on the same the L298 (granted it has serial control, but I'm perfectly happy to control the motors using a few digital Arduino ports.)
You might have a voltage drop of ~1-2v volts across that h-bridge, which is significant if you are using 4.8v for power. Try 6v and see if the motor works better. Have you measured the current the motors use when running? Could be several amps.
However, controlling the motor using the SN754410 bridge barely moved the motor.
You need to find out what is going wrong with this solution first. If the motor barley moved then it is likely that you have other problems such as the power supply. Did anything get hot? It should have.
While a LM298 is a better fit for what you describe, the SN754410 should definitely give you signs of life. In fact it should run fine as long as the motors are un-loaded.
My experience with these bi-polar motor controllers is that they rob a lot of power from the motors and make a lot of heat. They will get hot, start entering thermal shutdown and behave extremely erratically. Perhaps this is what you are seeing?
I would recommend a power MOSFET based motor controller which will run much cooler and put more power into your motor. There are several out there that would not break the bank.
Grumpy_Mike, the power supply is four 2500mAh rechargable AA batteries. There is no regulator, the SN754110 stayed cool. The batteries do not get hot. Arduino drives the +5 and control pins of the bridge and nothing warm there either.
Zoomkat, you maybe onto something... I measured the voltage across the motor, last night and it was only 2.9V! I'll try increasing the supply voltage tonight.
The L298 requires a heatsink for sure. 4A is optimistic, but if you have a heatsink the size of a barn door, they are theoretically designed to handle it. For my money they are crap though.
I chucked out my L298 controllers and put in VNH2SP30 based ones from Pololu and I couldn't be more happy with how they work. Pololu have controller boards based on that, the cheaper VNH3SP30, MC33887 and MC33926 and others.
The main down-side to the modern high tech power MOSFET based controllers is that they all seem to be SOIC SMT parts, so they are tough to breadboard around and you wind up having to buy a manufactured board.
Google around for H-bridge circuits designs using discrete MOSFETs too. You might find something that appeals to you.
