Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: Conscripted on September 23, 2012, 08:40:41 AM

Title: H-Bridge for Wally the Wall bot
Post by: Conscripted on September 23, 2012, 08:40:41 AM
Good morning all.

I recently purchased the book "Arduino Robotics".  Chapter 5 has a bot called "Wally the Wall-bot" that I'm interested in building. I was hoping some one here has already built the h-bridge. I would hate to purchase the parts, put it together and then spend a bunch of time debugging the circuit if it's a poor design.

I found a digital version of the schematic  HERE (http://books.google.com/books?id=tBdKnLcf2oEC&pg=PA173&lpg=PA173&dq=wally+h-bridge&source=bl&ots=eT5bm9fkG-&sig=lsKUFVmT2Uj4L4zBrgIyV4Ayr6o&hl=en&sa=X&ei=2FpfUJS2G4XD2QWntYHADQ&ved=0CCcQ6AEwAA#v=onepage&q=wally%20h-bridge&f=false). The page with the schematic says "175"
The circuit uses
The H-Bridge is stated to work at 18VDC, 5A continuous, and PWM at 32KHz.

Does anyone have any experience with this circuit?

Thanks.

Conscripted
Title: Re: H-Bridge for Wally the Wall bot
Post by: waltr on September 23, 2012, 05:18:21 PM
That H-bridge circuit is isn't too bad.
The major issue I have with it that both the low and high MOSFETs could be turned on at the same time. I call this the "Smoke' condition since it produces a short circuit.
Title: Re: H-Bridge for Wally the Wall bot
Post by: Soeren on September 24, 2012, 12:14:21 PM
Hi,

There's the possble current shoot-through as waltr mentioned and it strikes me as very odd and inconsequent using a MOSFET driver for just the low side and discretes (of a lower current handling capability) for the high side - I don't believe it's made by a pro.
Apart from that, it should work if controlled correctly :)
Title: Re: H-Bridge for Wally the Wall bot
Post by: Conscripted on September 24, 2012, 12:29:36 PM
Thank you both for your input. I was pricing the parts out and it looks like it will cost me about $25 plus shipping. Do you know of a better design that is comperable in price and specs?

Conscripted
Title: Re: H-Bridge for Wally the Wall bot
Post by: waltr on September 24, 2012, 07:56:21 PM
1- look up Soeren's posts. He his posted schematics of H-bridges in the past.
2- With all of the integrated H-bridge chip available I haven't build a discrete H-bridge in many years.  Search through threads here on H-bridges for some suggestions.
Also, google will help find others.