I have to control four DC motors (two channels) at maximum 490 mA, for this I need a H-bridge. Since I'm going to drive two motors per channel, I'll need around ~1 A per channel.
L293B: 1 A per channel, no clamp diodes.
L293D: 600 mA per channel, got clamp diodes.
L293D is probably too low rated, but the L293B doesn't have any clamp diodes. I know how you use clamp/flyback diodes with a simple DC motor (mono-directional), but I'm not sure how it works when using a H-bridge.
My last choice is to use two L293D's, but this seems kind of unnecessary.
Not a hundred percent sure that I'm reading this correctly, but am I required to use eight diodes on the L293?
Because if so, it might be much easier to use two L293D, perhaps.
Edit: But on page two it seems to be a little bit different (six).
Obviously I'm still learning.
I'm still working on exactly how the whole circuit will look like, but what's relevant for this is only how the motors are connected, as far as I know?
It'll simply be like this diagram here below, except that I'll add another motor in series on each side (A and B).
Now another question though regarding powering the L293B (Vcc1), and I seem to have three choices here.
(Page 5)
Recommended voltage: 4.5-7 V
Max current: 60 mA (typical 35 mA)
I'm going to power the Arduino with a 9 V battery.
The question is if I should use the Arduino Vin pin for the L293 Vcc1, or if I should use the 5 V pin on the Arduino.
Vin pin will be at 9 V, but I guess that would be safe as well?
And the 5 V pin might not be able to handle the (max) 60 mA.
Oh I see, wasn't aware of that. I do however have one (rechargeable) that I can use (and have used) for my Arduino. But now that you say it, hell, it's only at 200 mAh, while somewhat cheap AA batteries are at ~2k mAh.
A question about motors (while I'm at it). I read that
"It is important to note that you never should reach stall, which would cause a motor to burn out very quickly. You should design for about 1/4 stall"
The question is if I should then run the motor at 3 V (which seems a bit low), since then the stall current (1.5A) is below L293B max (noncontinuous, 2A) current. This also means that I'll need two L293B.
and especially something as expensive and inefficient as a 9V for your project.
well a 9v battery costs Rs.10(0.25 USD) are there batteries cheaper than that ? :-/ i guess batteries are expensive where you live
( and i didnt mention a duracell battery )
and again i know they are not good but just curisoty
A question about motors (while I'm at it). I read that
"It is important to note that you never should reach stall, which would cause a motor to burn out very quickly. You should design for about 1/4 stall
NO nothing like that !
The question is if I should then run the motor at 3 V (which seems a bit low), since then the stall current (1.5A) is below L293B max (noncontinuous, 2A) current. This also means that I'll need two L293B.
that depends ! you might or not reach that but its advided to have a motor controller of higher rating than required so.. connect them in parallel or mount one on another ( keeping the pins same ) and solder them
weell waht we have discussed so far is about h-bridge ic's ( they have a h bridge within them )
you could make your own !
google for it !
here is a link for one but will be more than you require
IMHO, designing the circuit for anything less than 2X the stall current is just ASKING for trouble. But then I am a conservative guy (in all definitions of that word.)
Why 2X (other than being "conservative") - why not perhaps, say "25 percent" more (I wonder if that is what "1/4" meant)?
I only ask this because I have some large motors (potentially 85A stall current!) on my robotics project I am planning on controlling with an h-bridge of some sort. Ultimately, I plan to purchase such a controller, but I was planning on something able to control about 100A of current (I can't afford much more). Also, I don't even think the main fuse nor the switches used originally on my platform (a Powerwheels H2) were even rated for 80+ amps (I think the fuse is only a 20-30A blade-type).
Anyhow - there's no way I could even think of affording an h-bridge controller for 160A or more (and I need two!); I'm already not liking the cost of the h-bridges I will likely purchase...
Anyhow - there's no way I could even think of affording an h-bridge controller for 160A or more (and I need two!); I'm already not liking the cost of the h-bridges I will likely purchase...
Osmc group seems to have motor controllers designed for high current requirements why not try them ?
Osmc group seems to have motor controllers designed for high current requirements why not try them ?
I've looked into them - I haven't yet decided what to use until I get to that point; I was just curious about the comment from a general standpoint.
Because, at least IMHO, at those power levels (Glaucous' project) it doesn't cost much more (maybe no more) to do 2X than 1X or 1.25X the stall current. That is just my gut feel for small quantity self-made, self-used, DIY projects, etc.
OK. For my steering motor, I was thinking about going with an bridged L293, but decided to use a bridged L298, since I have them on hand (for some reason, I have no 293s!) - even though in bridged mode they'll handle 3-4 amps (with a heatsink of course), and the stall current of my steering motor is in a 1A range (which I measured).
OTOH, for high-power projects like you are talking about, and/or if you are designing something for commercial production, then you must make these tradeoff decisions with more careful attention to cost/benefit and price points, etc. etc.
No - not thinking about designing or building such a beast, just buying one. I have still yet to verify the current usage of these motors (there are two of them), but I know that the protection fuse on the Powerwheels H2 is no where near what I think their current consumption at stall actually is (but is larger than the running current); this is based on a datasheet for a similar 550 motor at BaneBots.com that someone pointed out to me who had used a Powerwheels motor and gearbox to actuate a power-steering system for his off-road vehicle.
Once I get to working on the back-end drive system, I will know more; I am hoping to keep the costs low - high amperage brushed DC reversible motor controllers aren't cheap...
Okay I've made up my mind (and gotten the motors), and I'm going to build two H-bridges. Since there seem to be lacking any good H-bridges here in Sweden (I could import, again, but hey, this could be fun).
And the best thing to use seems to be MOSFET, since I then can avoid the flyback/kickback diodes.
Any special specification in MOSFET I should look for? As long as Drain Current and Drain Voltage is within range, I should be okay?
Problem might be to find a MOSFET with Vgs of 5V.
