I have a stepper motor that draws a current of about 1.5 amps, but I only currently have a l293D. The IC can only handle 1 amp, so I need to get another IC to replace it. Does anyone have any suggestions regarding what IC I should get (It has to be in a DIP package as I am breadboarding it).
If it is in a TO-220 package, it will also work
There aren't any that you can breadboard. Use a stepper driver module, like this one. Be sure to adjust the current limit according to the instructions.
Correct me if I am wrong, but lowering the voltage would allow me to also lower the current (as resistance of the coils cannot be changed). My project uses a 12V supply, and that cannot be changed. However, I have a 5V regulator (UA7805), which handles 1A. I suppose this would work because after the voltage is regulated down to 5V, the current draw would be under 1A (satisfying both the regulator and the l293D). Is this whole idea feasible?
There is an easy way to do this.... The L293 is a bit unique in this and you cannot do this with most other chips. Piggyback! Yes, just as the name suggests. Get a second L293 and solder it on top of the original one. I have a similar problem and I want to use my stepper motor at higher power levels and it works. I have 3 of these chips stacked like this and it works a treat. Just make sure that ALL the pins are soldered (and you have it the right way round, of course :confused: )
Oh yes, lift it out of the breadboard while you do it or you will melt the breadboard...!! :banghead:
Are you sure that's "legal" (as in it would work)? I thought electricity will try to take the path of least resistance, and no two ICs will have EXACTLY the same resistance. Therefore, one chip will take all of the load while the other will just not do anything. I know this is true for transistors, which is why you cannot attach then in parallel, but is okay for FETs. The schematic of the chip show that it uses transistors, not FETs. Then again, I don't know too much about electronics :P
Take a look at the first answer in this thread. Does that mean I can just put one on top of the other, or do I have to do some fancy wiring to make it work?
As I originally said, you can't normally do this with most chips, you would need to 'help' them to balance with emitter resistors or similar. But these chips are not super high power. Yes, they use bipolar transistors, not FETs. These are monolithic ICs and will balance close enough for the power levels we are talking about here. Just to help them out, add a small amount of heat transfer compound to the plastic where they contact each other. Dissimilar temperatures can cause saturation imbalance but the pins are going to be soldered together anyway.
A pair of 'unbalanced' bipolar transistors would not see one with no current and one with all the current but you might get a 60/40 or even a 70/30 share. What would be likely to kill them is when they heat up. The higher current device would then heat more and saturate lower.
So would it be a bad idea to put a heatsink on the top chip as it would cause a larger temperature difference between the two (even with thermal paste between them)?
Piggybacking sounds like a lot of effort and "hope for the best", to avoid paying $8.95 for a modern motor driver module, with vastly improved efficiency and other handy features like microstepping.
I think this setup works well enough so long as its works. Plus, I already have a few spare L293D's lying around, so I will use that method.
At the cost of these chips, it would be better to use 3 not 2, probably cheaper than a heatsink..
That true, but I might as well use a heatsink (mostly because I have a bunch from old electronics that are just lying around - they serve less function than the chips, so I would rather be conservative on my use of the chips). :P
However, I have a 5V regulator (UA7805), which handles 1A. I suppose this would work because after the voltage is regulated down to 5V
You can try it, but...
The motor may nor run, or it may not run reliably at 5V.
Linear regulators like the 78xx don't have a "simple" current rating. They can overheat at less than 1A. Power (related to heat) is the product of Voltage X Current. With 12V applied to a 7805, the voltage regulator will be dissipating more power than you are delivering to the motor (with 7V across the regulator, 5V across the motor, and the same current through both).
I'm not saying it won't work, but you may need a heatsink. Or, you might need a different regulator, maybe (much more efficient).
....I had an overheating 7805 (at around 1/2 Amp) and I used a couple of "stupid tricks" to get around it, but the longer-term plan is upgrading to a switching regulator.
All the suggestions so far have been good except the idea of using an LM7805 to drive a stepper motor. Forget that idea now. For it to be even marginal, you would have to use a very good TO220 Heatsink. You be better off getting one of these
I think I am just going to go with the stacking the chips idea. It seems the fastest way to do this (as long as it works, it is not really crucial how I do it). Thanks all!
If you can get some clearance between the stacked chips and add a small fan that would help dissipate the heat.
So I would not want to put thermal paste between the chips as suggested before?
Thermal paste is intended for use whenever you have direct contact between the heat generating device and the heat dissipating device. Using thermal paste between two chips in direct contact with each other does not have any benefits because they are both heat generating devices and not heat dissipating devices (such as a heatsink) I would guess there is no way to solder the pins of one chip to the pins of the chip it is sitting on without placing them in direct contact because the pins would not reach otherwise. Personally, I don't like that method. The objective is to connect all the pins of one chip to the same numbered pins of the second chip. There is nothing that says they must be stacked on top of each other. In my mind, the proper approach is to simply go to RadioShack and buy a through-hole plated pad for pad proto board and line the chips up on the board and solder wires between them using the through-hole plated pads and solid copper 20 guage or 22 guage hookup wire. I would actually use sockets so I can replace a chip if need be. You wind up with a "motor driver bus" with a bunch of wires that then plug into the breadboard, The motor driver is now a double or triple driver on a separate board with socketed chips. You can then get a small fan and cool the entire PCB (which will be sharing the heat). Stacking the chips has it's place when it is called for but I would hardly call that the "proper" way to do it. If you stack the chips and the one in the middle blows, it is more trouble than simply replacing a a socketed chip. Yeah, so you have to some soldering but if that's too much trouble then maybe you should find another hobby.