driving (inputting) the L9110s H-Bridge.

Thread Starter

cornishlad

Joined Jul 31, 2013
237
Project is an electro/mechanical clock the closes a contact every 30 secs. I wish to connect it to a dial mech that requires a pulse of alternating polarity every 30 seconds. Yesterday I cleaned up the the pulse with a 555, and with the aid of a 4013 & 4011 produced the neccessary drive pulses. ( about 300 Ms) All working on 5v. The H bridge was on a small Chinese module. I got no output from it to the clock motor.
Spent a long time testing.. Put LED's on the output of the driver circuit indicate it works.
A 6v bulb on the output of the H-bridge indicates that it responds to test inputs on wires to the 5v supply. I'm stumped.
Any theories or experience driving this chip appreciated.
 

WBahn

Joined Mar 31, 2012
27,946
Could you post a link to the data sheet for the H-bridge module?

Are you driving the module's input directly from... what? The 4013? The 4011? A schematic would sure help.

Also, 300 Ms is just a bit shy of ten years. I'm guessing that's not what you meant.
 

Thread Starter

cornishlad

Joined Jul 31, 2013
237
Here's the circuit of the driver. It's a circuit I used 7 years ago in another clock that's worked faultlessly ever since. The h-bridge module was a different one though. The clock signal comes in via the 555 monostable which is another module by Mitch Electronics. Standard circuit I imagine.
 

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Thread Starter

cornishlad

Joined Jul 31, 2013
237
In the driver circuit above I accidentally left in the clock as 1pps. That was as was in the design I copied.. but of course in this case its 2 pulses per minute.. sry ..very old brain at work ! R
 

Jon Chandler

Joined Jun 12, 2008
440
I don't know if this makes a difference in your circuit, but the L9110 has a unique feature compared to other H-bridge chips.

If both inputs are LOW, both outputs are LOW.

Unlike other H-bridge chips however, if both inputs are LOW, both outputs are also LOW, rather than HIGH as you'd expect.

I don't remember exactly what I was working on when I found this quirk.


Screenshot_20221023_213631_Dropbox.jpg
 

Thread Starter

cornishlad

Joined Jul 31, 2013
237
Hi.. Sorry for delay.. I gave up on that project for a while while I waited for a replacement H bridge module to arrive.
Jon.. I think you meant if both inputs are HIGH.... as per the circled truth table ! However the driver circuit should alway present 2 lows except when a high pulse appears alternately on 1A and 1B.
Anyway.. now it now all works !! The replacement H bridge made no difference. I'm not sure if it was the main culprit, but the 555 monostable on the system 5v supply only sent a HIGH to the 4013 that was marginal as a cmos signal.
Also ( and maybe because of that ) the 4011 output drives were less than 3v (but enough to light a green led) The whole thing was on a breadboard so an intermittent connection can't be ruled out.
I replaced the 4011 and upped the sytem supply to 9v - but dropped the supply to the cmos driver board by about 2v via a red LED
Now all works fine. I haven't the patience to go back to the original setup stage by stage to actually confirm where the problem lay ;-) Thanks to all who replied.. Roger
 
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