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LBHSroboGuy
04-08-2010, 09:35 AM
Ok I'm trying to use a Hall effect sensor and an H-Bridge to make a brush-less DC motor, I got the Hall effect sensor working, but I'm having trouble getting the H-Bridge to reverse the current could someone help me out some, I think I'm miss reading the Datasheet I got with the H-Bridge, I'm not that great at reading very technical schematics.

I'm using the Basic Stamp from my boe bot kit, and what I have set up is-

H-bridge Basic Stamp
Pin 1------>Pin 15
Pin 16---->VDD
Pin 8------>6V Battery
Pin 5------>GND for 6V Battery

I've been a bit confused as to how exactly the motor terminals should be plugged, but I've been testing it out by trying it with an LED, but I can't seem to get the LED to light up in either direction, yes I know LED's only work in one direction so I tried flipping the terminals when I tested it out.

Here's the link to the Data Sheet. www.sparkfun.com/datasheets/IC/SN754410.pdf (http://www.sparkfun.com/datasheets/IC/SN754410.pdf)

Franklin
04-08-2010, 11:36 AM
Show us your code. Also you need more hooked up to reverse the motor and a circuit diagram would help.

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- Stephen

Lucky
04-08-2010, 12:47 PM
What you have here is a Quad HALF H-Bridge. This means you need to use two halfs to get a full H-bridge which is capable of forwarding and reversing your motor. So this means that you would put one motor lead on Y1 and the other on Y2. To make the motor go in one direction, apply a high to A1 and a low to A2. To makeˇit reverse, make A1 low and A2 high. Note also that the Enable pin for that side of the IC has to also be held high in order for the two half H-Bridges to work.ˇSince this is a Quad, and it takes two halfs to make a fully functional whole, this IC can drive two motors in both directions. The datasheet also mentions using a separate powersupply for the logic inputs (Enables, and A1, A2) soyou can hook thosepins directlyto your Stamp,justmake sure that the motor runs off a separate power supply(do this by attaching a different battery pack to the ICs Vcc and Gnd)

The attached picture shows what happens internally to make your motor turn in both directions. The IC is basically switching the direction of the current through the motor to make it turn a different way

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"The man who smiles when things go wrong has thought of someone to blame it on."


-Lucky

Post Edited (Lucky) : 4/8/2010 5:52:14 AM GMT

bill190
04-08-2010, 10:39 PM
As an additional source of information, the following discusses H bridges about 1/3 of the way down the page when used with stepper motors for automobiles (Idle Air Control [IAC]ˇvalve)...

http://www.megamanual.com/ms2/IAC.htm

Main page to the above...

http://www.megamanual.com

LBHSroboGuy
04-10-2010, 10:19 AM
Lucky said...
What you have here is a Quad HALF H-Bridge. This means you need to use two halfs to get a full H-bridge which is capable of forwarding and reversing your motor. So this means that you would put one motor lead on Y1 and the other on Y2. To make the motor go in one direction, apply a high to A1 and a low to A2. To make it reverse, make A1 low and A2 high. Note also that the Enable pin for that side of the IC has to also be held high in order for the two half H-Bridges to work. Since this is a Quad, and it takes two halfs to make a fully functional whole, this IC can drive two motors in both directions. The datasheet also mentions using a separate powersupply for the logic inputs (Enables, and A1, A2) soyou can hook thosepins directlyto your Stamp,justmake sure that the motor runs off a separate power supply(do this by attaching a different battery pack to the ICs Vcc and Gnd)
The attached picture shows what happens internally to make your motor turn in both directions. The IC is basically switching the direction of the current through the motor to make it turn a different way


Thanks so much, this really clarified it for me, and it worked, I was able to get the LED to work, so now I just have to set up the real circuit. http://forums.parallax.com/images/smilies/smilewinkgrin.gif