Date: Fri, 4 Mar 94 13:33:59 EST From: John_Cook_at_USNUS08@usnus05.usnus.abb.com To: Multiple recipients of list Subject: How to Build an H-Bridge Hi all, After much burrowing in catalogs & data books I found a way to replace the L293s on my 6.270 with something better thats easy to get and build. Teledyne sells some power MOSFET drivers that have enough continous curent drive to be able to drive motors and Digi-Key carries them. The TC4421/2CPA is an 8 pin DIP designed to drive MOSFET gates and other reactive loads quickly. Its got a 9 amp peak and a 2A continuous current drive, input hysteresis, back EMF protection, low power loss, and runs on TTL or CMOS level inputs. Use a pair of them as an H-Bridge if you connect a motor or other load between them. Add a pair of NAND gates for control logic. Enable input goes to both NAND gates and a direction line goes to the remaining NAND input. You now have one enable line and two direction lines, just like the L293. Put both TC4421's in a 16pin socket, add a slide on heatsink, some bypass caps and you're in business. It only takes 3 chips and some bypass caps to get higher output, noise immunity and MUCH lower power loss than the L293. Cost: about $12 per H-bridge. Have fun! -John C. ABB Nuke Operations. Date: Fri, 4 Mar 94 16:39:45 EST From: John_Cook_at_USNUS08@usnus05.usnus.abb.com To: Multiple recipients of list Subject: Re: How to Build an H-Bridge Schematic? no problem! Dir A ---------------- Nand-------Driver====Motor====Driver ----- | | | | | Dir B ------------(--- | | Nand ----------------------------- | Enable --------------- If its not clear, Dir A and Enable go to one Nand gate whose output drives the left side driver. Dir B and Enable go to the other Nand gate whose output drives the right side driver. To operate it, make Dir A HIGH, Dir B LOW, and Enable High, motor spins one way, reverse Dir A and B, motor spins other way. Make Dir A and B the same or make Enable Low, motor stops. To integrate it into the original 6.270 board, pull out the original DIP socket for the L293 for either motor 0 or motor 1. Install a pair of snappable strip sockets like all the others used on 6.270 and make headers to match. On the expansion board or on a separate board build the above schematic, adding a 1 uF decoupling cap to each driver IC. I'm putting them both in a 16 pin DIP so I can use one slide-on heat sink from the original L293s. You'll also need to build a cable to carry the signals meant for the L293 to the new circuit. Enjoy! -John C. ______________________________ Reply Separator _________________________________ Subject: How to Build an H-Bridge Author: Kurt Konolige at SMTPLINK-USNUS05 Date: 3/4/94 12:09 PM Yes, but...how about a schematic? And how do you integrate them into the 6.270 board? Just curious --kk Date: Mon, 7 Mar 94 09:38:29 EST From: John_Cook_at_USNUS08@usnus05.usnus.abb.com To: Multiple recipients of list Subject: Re: How to Build an H-Bridge You know, I asked around some more and Digi-Key sells a National LMD???? part which is a complete H-bridge in a TO-220 package. Theirs is 3A @55V with thermal protection but it costs about $20 per part! Good luck! -John C. ______________________________ Reply Separator _________________________________ Subject: How to Build an H-Bridge Author: Kurt Konolige at SMTPLINK-USNUS05 Date: 3/4/94 2:03 PM I was afraid it was something like this, instead of just a replacement on the original board. Not too bad, though. THanks for the tip. --kk