Home made H-bridge...
Howdy...
I just designed my first PCB and had it manufactured by Dorkbot PCB.
Took a couple of weeks to get the boards but I think they came out great.
Specially if you like purple boards... ;-)
The design itself is an H-bridge taken from Chuck McManis site,
http://mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-circuit.html
I replaced the Tip 102/107 with the more powerful Tip 142/147 and skipped the protection diodes since they are built in in the Tip 142/147.
For opto-couplers I used the PS2501-4 since I already had a few of them laying around.
The switching speed for the opto-coupler is 5us so with 128 distinctive steps I calculated the PWM frequency to 1.5KHz.
You can clearly hear the motor "sing" when using this PWM frequency... ;-)
It was a great fun project and I definitely designing some more PCBs in the future...
I just designed my first PCB and had it manufactured by Dorkbot PCB.
Took a couple of weeks to get the boards but I think they came out great.
Specially if you like purple boards... ;-)
The design itself is an H-bridge taken from Chuck McManis site,
http://mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-circuit.html
I replaced the Tip 102/107 with the more powerful Tip 142/147 and skipped the protection diodes since they are built in in the Tip 142/147.
For opto-couplers I used the PS2501-4 since I already had a few of them laying around.
The switching speed for the opto-coupler is 5us so with 128 distinctive steps I calculated the PWM frequency to 1.5KHz.
You can clearly hear the motor "sing" when using this PWM frequency... ;-)
It was a great fun project and I definitely designing some more PCBs in the future...
Comments
I like this H-bridge design, It seemed to be more "Tommy Proof" then some of the others I looked into.
It has lots of power for the little Roomba motors I am using.. I have to hold both in a stall for the transistors to get warm.
I used a single sided board, and made it the same size as the Prop Proto board.
And I went with the 120/125 darlington's, and all I had at the time was some 4N26's for the Opto's.
Good work, Thanks for sharing.
-Tommy
They seem to be pretty "Fredrik Proof" as well, I managed to short them out a couple of times and my power supply shut down.
A quick reboot of the power supply and the H-Bridges keeps going... ;-)
The Tip142/147 are rated 10A and the Roomba motors stall current is 4A so I got room to spare.
Here is a video of the two of them in action.
I'm controlling the Roomba motors with a cheapo Nun-chuck I got from E-bay.
http://www.youtube.com/watch?v=I0RZbAHI1jY
You can clearly hear the motor "sing" at 1.5KHz frequency.
But 10A is a big plus of course...
The L298 should be more than powerful for my Roomba motors, Solarbotics sell a motor driver with this chip for $19, pretty good price.
I just measure the motors to draw 200ma when idling at full speed.