Well my reasoning here was that an l293 or sn754410 is actually a quad HALF-h bridge. So it can drive 2 motors in both directions, or 4 motors in 1 direction. In this case I have wired it so that it possible to use it either way, and have connected my 2 drumsticks so they are only driven in one direction, and I allow the springs to return them upright. I could in theory have up to 4 drumsticks with this board. I probably would have been simpler to just use transistors as you did with LDM, but I liked soldering using the socketed chip, cuz the protoboard I used allowed me to do essentially through-hole on this board, and the IC made sense. ALso, I happened to have it around from my dead pololu motor controller, and the h-bridge chip worked so I figured why not use it.
Oh, sure, if you’ve got them on hand then using these chips works just as well as individual transistors, and maybe better. I wasn’t trying to correct you or anything, my post was just aimed at MaltiK who didn’t understand how five motors could be driven by only one chip. I was just explaining that at least in Frits’ and my robots, the H-bridge chip had only been used for the sonar motor. I just used regular 2N3904 transistors for the drumsticks, and if I remember correctly, Frits used the Darlington array on his Picaxe board. Using the half H-bridges on an L293/SN754410 is a third, valid alternative, but then yes, you’d need two chips.
We all need to build drum We all need to build drum bots, and then a year from now we can have an LRM meetup somewhere and have them all play at once!!
What are you using to power What are you using to power it? Are you using it on a project board or did you sodler something? Could be a short… They do get warm when you use them.
Higher current motors? Might need an L298 (here or here) or bigger, any specs on the motors? Measuring resistance across the motor terminals while turning slightly can get you a number to use with Ohms Law for stall current draw.
When i use it with a 7.2v battery its fine, but i have a 13.8 power supply that i have been trying to get it all working with. Its when i use that that things go wrong.
thats the power supply, its the M20W one. I am using a regulator with it too.
Im stil new to all of this, ive tried measuring amps and current but im somewhat baffled by it all. I kinda get it but then i cant apply what i think i understand of it all.
is the 13.8 power supply an is the 13.8 power supply an unregulated wall power supply? If so without a load it is likely supplying 15-16 volts and the amperage is too high.
Another clue mentioned was that the h-bridge operates fine at 7.2 volts, but gets warm at 13.8 volts. The motor winding resistance will be the same in either case. As an estimate, say the motors are pulling 360 mA (for easy math) from the 7.2v. That would give the motor resistance to be 20 ohms (ignoring transistor losses) by the V= IR changed to V/I = R formula. So if you increase the voltage to 13.8v, the motor coil will always be 20 ohms, the current becomes 690 mA from the formula V/R=I. That 690 mA is above the continuous current rating of the L293D, which would be a good reason why it is heating up.
Is there some device you are wanting to add to the tank base that requires 12 volts? If not, why not just use the 7.2 volt pack?
Theres nothing that needs that much power, the reason i wanted to use the 13.8v supply was so that i could get some decent programming time without being restricted to however long the battery lasts. My plan was to use a long cable i have from some garden lighting to feed power to him permanently.
I may have to rethink my strategy though and just buy another power supply that is adjustable.
