NI$HANT:
I would suggest if you aren't able to procure these under defined H-Bridges then try out making your own, here is a very good tutorial >> MOSFET H-Bridge Motor Control using power Mosfet's.
That's not a bad tutorial; the only problem is sourcing the p-channel mosfets (can be done fairly easily if bought new from places like mouser and digikey, but for some reason, buying p-channels from ebay or surplus isn't as easy, at least ones matched in performance to the n-channels; I think this has to do with costs, as n-channel mosfets tend to be cheaper, plus for h-bridges at least, the easy availability of drivers/charge-pump ICs for all n-channel designs). But - if you can get the parts, they tend to be easier to build.
NI$HANT:
also even if you want to use small hobby motors like the ones futaba makes and are also found with TAMIYA hobby kits(i have one of them)then in that case also they call for a lot of Amperage to be handled you have to use the D -cell method to calculate the H-Bridge value before buying or even making one.
Or use a bench/lab power supply (for really large motors, you have to get creative - I have a car starter/battery charger that I use for anything needing 10 amps or more).
NI$HANT:
You have to go like 1) Hold the multimeter at DC amp level and put the + lead and - lead of the multimeter with your motor leads and power leads.
- Hold the movement shaft of the Motor from front and do not let it move and power it
If you're going to describe this process, be clear about it (otherwise damage to the meter, motor, or user is a possibility):
-
Put your multimeter in current measurement mode; most meters can handle up to 20 amps, but check your meter (put the leads into the proper jacks on the meter, if the meter has separate high-current jacks).
-
The meter needs to be placed in series with the load being measured: So, positive from supply to load, other side of load to positive of meter, negative of meter to supply ground.
-
Mount the motor so that the body can't spin; grip the shaft so it can't turn (note: on larger motors, DO NOT try to do this with your hands/fingers; fabricate a pony-brake test stand instead).
-
Verify that when power is applied, nothing is going to start spinning and fly off and whack you in the head.
-
While reading the meter - apply the power BRIEFLY, and note the current measurement. Do this a few times, but each time very briefly.
The reasoning for step 5 is the fact that you are, in effect, "abusing" the motor and the meter; if you do this for more than a second or so at a time (and on larger motors, potentially less), you can easily burn out windings, and in the case of the meter, blow a fuse or otherwise burn out the meter (it's current measurement design isn't likely designed for constant high-current measurement in this kind of situation). Generally, you should do this kind of test with an el-cheapo throwaway meter from some discount tool vendor (like Harbor Freight), and not with your "good meter".
NI$HANT:
while the multimeter is there it will show you the STALL current for the motors you have and as per that you have to choose the building mosfets or ready made H-bridge IC's for your implication telling you the highest current soaking that can happen in the worst case scenario's.
Another method would be to build a pony-brake test stand with an adjustable slip fitting, such that the shaft can still turn, but just barely; this will give you a "heavily loaded" stalled reading; just add 10-15 percent for fully stalled (and that will also give you some breathing room, too).
NI$HANT:
I used 4 L293D's by STACK SOLDERING them one over one and thus multiplying there original power.
I've read of people doing that with two, but only guesses at doing it with four. To be honest, I'm surprised even two work. There are a couple of reasons why:
- Lack of cooling capability - L293s radiate heat from the center set of pins, and the top of the package; stacking them means the ones on the bottom can't effective cool themselves properly...
- BJT outputs - the L293 (and L298) using BJT (bipolar junction transistors) on the output stage; such transistors typically can't be paralleled properly (just like diodes), and the load won't be shared evenly on high currents. What happens then is a cascade failure. It is also why both h-bridges aren't very efficient, as compared to mosfet bridges (I'm surprised they've never release drop-in compatible mosfet designs for the L293 and L298)...
...and yes, I know it probably works for you, and its worked for others - why or how you get away with it, I don't know; I've never found a good explanation for it.
,well you have been specific im fine with that.