Help with dual h-bridge IC

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Help with dual h-bridge IC

Postby traltixx » Tue Feb 17, 2009 4:17 am UTC

Hi,
I have a DC motor that runs at 3V,150 mA (20 Ohm) and I was wondering what Dual H-bridge IC would be suitable for this? I was looking at L293D H-Bridge but it doesnt seem to be able to give the proper power. Any ideas?
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Re: Help with dual h-bridge IC

Postby matteh99 » Tue Feb 17, 2009 1:05 pm UTC

The specs I found on that chip say it should be able to handle 600ma continuous so it should work fine with your motor. I also found these chips a while ago which might make things easier for you http://www.national.com/mpf/LM/LMD18245.html . I haven't gotten around to doing any thing with them yet but I ordered them as samples. Free samples are awesome :)

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Re: Help with dual h-bridge IC

Postby ATCG » Wed Feb 18, 2009 2:03 am UTC

Take a look at some of the offerings of Allegro MicroSystems, particularly the A390x series. It's purpose-built for your application. I think the A3901 could turn out to be a good fit for you; unlike the L293D, it can make it down to the 3 volt output you require.

The downside to Allegro is that their parts can be hard to find in less than tape-and-reel quantities, and I suspect you don't want to buy a thousand pieces at a crack. Newark, though, has - at time of posting - 793 pieces of the A3901 on the shelf for $0.937 each (quantity 1-24, Newark part number 87K3379). Less than a buck is not bad for two full H bridges.

Now for the bad news. These parts are only available in dinky surface-mount packages. Unless you have the dexterity of a microsurgeon (and tools to match), I would recommend an IC package adapter (you want the E11-0090 down toward the bottom of the page). It's not ideal: the pad on the bottom of the IC package should really tie to a large copper area for heat dissipation, but I don't see you dissipating more that 140mW in this part with two motors on (assuming you don't exceed 150mA/motor) which ought to keep its temperature rise below 30ºC. The adapter is $7.75 and for another $8.25 they'll solder your part onto the adapter for you, so for only 18x the price of the naked driver chip (or roughly $8.50/motor), you'll have something you can actually use.
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Re: Help with dual h-bridge IC

Postby traltixx » Thu Feb 19, 2009 2:31 am UTC

Thanks for the replies,
http://www.national.com/mpf/LM/LMD18245.html seems to be abit too much for me. They are 55V at 3A.
And as for the A3901 seems very much ideal except I might end up asking/paying someone to solder it for me and I can't breadboard it as is,right?
Anyway, thanks again
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Re: Help with dual h-bridge IC

Postby ATCG » Thu Feb 19, 2009 3:45 am UTC

traltixx wrote:And as for the A3901 seems very much ideal except I might end up asking/paying someone to solder it for me and I can't breadboard it as is,right?

Well, you're looking at an IC package that is 3mm x 3mm with 5 lands on a 0.5mm pitch on each of two opposing sides, plus a thermal pad on the bottom. I won't say that it is impossible to work with. I know (and contract with) people with both the hand/eye coordination and the equipment to tack wires and a heat sink onto one of these in maybe five minutes. But it takes skill and tools beyond those of the average hobbyist.

Perhaps someone here on the forum has a good DIY technique for working with fine-pitch parts like this. As for myself, I cross someone else's palm with silver and make it their problem.

traltixx wrote:Anyway, thanks again

You are welcome. Good luck.
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Re: Help with dual h-bridge IC

Postby traltixx » Thu Feb 19, 2009 11:45 pm UTC

yeah, looking at the dimensions make me feel like i might to assemble my lego mindstorm somehow to do it for me.
Also, i have a broken pc (mainly motherboard and CPU) and a disassembled all in one scanner/printer (that I took apart myself to canibalize its stepper motors) and I was wondering if these devices have dual h-bridges on them? I'm guessing the printer might have something but how do I tell which is which? I can barely read off whatever is written on the IC.
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Re: Help with dual h-bridge IC

Postby phillipsjk » Fri Feb 20, 2009 6:19 am UTC

Stepper motors will not be driven by an H-bridge. Those motors are pretty much designed to simplify the controller (not needing position feedback).

You need to find the chip controlling a brushed motor like the one you are using. (follow wires/traces)

On working with SMT chips:

The first step is to get a fine tip for your soldering pencil. You may want to use solder that has a narrow plasticity range such as 63 37 (Tin/Lead) solder. With RoSH, people are trying to move away from lead-based solders though.

A quick google search reminded me that you need flux paste for SMT work as well.

One Trick I heard for bread-boarding SMT chips is to solder fine wires to them. To do this, You would tin the wire, then heat it up while in contact with the pad. In use the chip would actually be laying on its back.

I have not tried it, but I have used a similar technique for joining two wires: Tin both ends; heat while holding them together. If you don't jiggle too much, you have a nice strong connection.
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Re: Help with dual h-bridge IC

Postby traltixx » Sat Feb 21, 2009 5:05 am UTC

Wierd, I had to get some form of H-bridge to run my stepper motor from my microcontroller because thats what the microcontroller wasn't able to provide enough power. Anyway, I can't seem to trace them in general because its too small.
And thanks for the tips on the SMT chips....hmm, it does look like I'll have to build a 3rd hand thingy out of my lego mindstorm to keep precision...thanks again
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Re: Help with dual h-bridge IC

Postby phillipsjk » Sat Feb 21, 2009 9:58 pm UTC

Well, discrete devices called "Transistors" can help with that. An H-bridge chip just has several, with safety circuitry in a single package. Power transistors tend to have a built-in diode to allow a current path to suppress voltage spikes from the motor.

Discrete components would require extra components like resistors though. FETs need a resistor between the gate and source to protect against ESD (also used to pull the transistor fully off).

FET=voltage driven
PnP/NpN transistors=current driven.

Driving something like a relay may also require transistors.
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