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Motor Control with SN754410 — Parallax Forums

Motor Control with SN754410

LSBLSB Posts: 175
edited 2006-04-22 23:10 in Robotics
I'm having a dickens of a time and am hoping some more experienced technician can point out where I've missed the boat.

I have two tiny Maxon gearheads I'd love to see work with my Boe-bot, so... I bought a few SN754410's. Looking at the datasheet I see that no external components are needed and they'll drive a 500 milliamp load with 3 output lines (two, I think, with an inverter). I hooked up the motors to a 6V R/C battery and turning--no load--I get about 2-3 mA, well in the range of the SN754410 (even if I can't read an ameter and am off by a factor of 100).

Next step: Wire same 6V battery to Vcc2, ground 4 center pins, make sure of a common ground. Wire up to BS2 P0 to EN1,2, P1 to 1A, P2 to 2A. SET P0 and P1 HIGH, P2 LOW. Plug in BS2 and tah-dah... nothing.

Next step: OK, wiring error--check, recheck, and check again. Get out VOM and verify EN1,2 is HIGH, one half of input is LOW and other half is HIGH. Yep, but nothing on output pins (few floating .00Xs, but no output).

Next step: I'm not beaten, I understand "learning curve", it must be a programming error and though everything looks right something is obviously wrong. Wire EN1,2 directly to regulated +5 with one half of bridge and wire other half direct to ground. VOM shows same--no output. Something is bad... Try again with new BB, new wires, and new outlook.

Next step: Its a power issue, need more juice. A 1 amp regulator--same result. Too much power, I fried the chip, new chip and same result. LEDs work in place of SN754410, I've checked, rechecked, and triple checked everything I can think of... Motor runs fine at 1.5 volts and directly from the battery, but NOTHING will coerce any of the chips to give up a single milliamp on the output pins. The chip doesn't get warm; it doesn't do anything, but sit there on the board like 4 cents worth of sand.

ANY ideas? Are these chips super-sensitive to static or frustration? What am I missing here?

Thanks for ANY ideas.

Comments

  • BamseBamse Posts: 561
    edited 2006-03-29 03:48
    LSB,

    I am using the SN754410 to control my Lego Mindstorms motors, I used the following·diagram to hook it up:

    http://www.bio-bot.com/privateweb/datasheets/powercontrol/SN754410app1.htm

    The chip seem to be pretty forgiving since I manged to short the outputs a couple of times and it still works... rolleyes.gif


    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    /Bamse
  • LSBLSB Posts: 175
    edited 2006-03-30 00:57
    Thanks... Your diagram did the trick. For some reason I thought Vcc1 was output to uP and didn't wire it up. One look told me what reading the datasheet didn't... Thanks again.
  • BamseBamse Posts: 561
    edited 2006-03-30 02:57
    I cannot really take credit for the diagram since it's not mine...cool.gif

    Glad it worked for you...

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    /Bamse
  • Jared5755Jared5755 Posts: 26
    edited 2006-04-22 23:10
    There's an error in the diagram linked to above. It shows 2 pin 14's on the SN754410. Vss should go to 4,5,12,13 not 4,5,13,14. It's obvious, but I thought I would point that out just in case.
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