Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: javafiend on August 10, 2008, 12:35:28 PM
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Can anyone tell me the difference between a half h-bridge, full h-bridge, and dual h-bridge? More specifically, what they're capable of and why they're named like they are.
Appreciate it, thanks!
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My understanding is:
1. A half H bridge controlls one motor lead
2. A full h-bridge controlls two motor leads - and hence one 'full' motor
3. A dual-hbridge controlls two 'full' motors
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half h bridge is what the industry refers to a push-pull driver. this kind of thing can both source and sink. easiest to think of it is a npn and a pnp, with bases in parallel and emitters shorted.
a full bridge has two push-pull drivers. turning one to sink and one to source yields a motor direction, reversing their logic reverses motors directions. used to reverse current direction.
a dual h bridge has two h bridges, or four push-pull stages.
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So if I wanted to run 2 basic DC motors of a differential drive robot I would need a dual h-bridge, correct? Is this what other folks use? Also, what other options are there?
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your options are dependent on your application.
If you just want to drive two small motors (1-2 amp) I would recommend an l298 dual h bridge. I just built the circuit last night and it works great. I like the l298 because it is versatile. My purpose for using it was to drive a bipolar stepper motor but I can also use it to drive 2 dc motors instead . The chip is a tad difficult to solder but its not too bad.
For bigger motors I use a sabertooth 2x10 from dimension engineering. The thing was a bit pricey, but it has tons of features that I can use for all my future robots.
hope that helps
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So if I wanted to run 2 basic DC motors of a differential drive robot I would need a dual h-bridge, correct? Is this what other folks use? Also, what other options are there?
Checkout my motor driver tutorial for various circuits:
http://www.societyofrobots.com/member_tutorials/node/159 (http://www.societyofrobots.com/member_tutorials/node/159)
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Wikipedia has a good short description of H-bridges.
http://en.wikipedia.org/wiki/H-bridge (http://en.wikipedia.org/wiki/H-bridge)
I'm partial to the LMD18200 H-bridge IC. It uses MOSFETs so it doesn't get really hot like the L298 (which uses bi-polar transistors and provides a significant voltage drop to the motor). It also has built in flyback diodes, so you don't need external diodes like with the L298. The disadvantage is that there is only 1 H-bridge per package, whereas the L298 has 2 (a dual H-bridge). This makes the L298 cheaper to use. So I recommend the LMD18200 for 2 or 3 amp loads and the L298 for smaller loads like 1A or less.
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Checkout my motor driver tutorial for various circuits:
http://www.societyofrobots.com/member_tutorials/node/159 (http://www.societyofrobots.com/member_tutorials/node/159)
On the 600mA version you mention using the SN754410. After Googleing the part it calls it a Quad Half H-Bridge IC. I have no clue what that means, but I'm going to assume that it's a dual h-bridge (4 half h-bridges). However, I wasn't quickly able to find a simple diagram for using it. Now notice I said "simple." Is there anything like Admin's $50 robot tutorial for building an h-bridge with or without that IC?
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The SN754410 is a pin-for-pin replacement of the L293D - so you can use my L293D circuit diagram and choose which of two chips you want to use - there are NO changes. The SN754410 tends to be cheaper to buy and can provide a slightly higher current.
The SN754410, just like the L293D, is a Quad Half H-Bridge. Each 'Half' drives one motor wire. 'Quad' means 'x4' - so it can control 4 motor wires - ie 2 DC motors.
You can download the SN754410 datasheet here http://www.datasheetcatalog.com/datasheets_pdf/S/N/7/5/SN754410.shtml (http://www.datasheetcatalog.com/datasheets_pdf/S/N/7/5/SN754410.shtml)
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Wikipedia has a good short description of H-bridges.
http://en.wikipedia.org/wiki/H-bridge (http://en.wikipedia.org/wiki/H-bridge)
I'm partial to the LMD18200 H-bridge IC. It uses MOSFETs so it doesn't get really hot like the L298 (which uses bi-polar transistors and provides a significant voltage drop to the motor). It also has built in flyback diodes, so you don't need external diodes like with the L298. The disadvantage is that there is only 1 H-bridge per package, whereas the L298 has 2 (a dual H-bridge). This makes the L298 cheaper to use. So I recommend the LMD18200 for 2 or 3 amp loads and the L298 for smaller loads like 1A or less.
Just for info: if you get the L293D then it DOES contain the external diodes.