I don't have the book so I can't comment on whether the circuit is correct -
so for now lets assume it is.
Can you explain in more detail how the 74HC244 is connected to your H bridge
and a little more detail about how the AVR is connected to the 74HC244.
If I understand correctly, you power the motor via the H-bridge from the 18V
battery, but how do you power the 74hc244 and the micro? Are you using a
pre-built PCB for the micro etc or is it had wired?
I hope I don't insult you (I am VERY impressed with what you have working
this far) but I hope that you are not trying to power the 74HC244 of the
drill battery as well - that would be a bad thing to do - it is rated at max
7v (5V typical) so I am would not be surprised is the chip is melting.
HTH
Ivan
Sydney, Australia
----- Original Message -----
From: "Ben Matthews" <mben12@gmail.com>
To: <AVR-Chat@yahoogroups.com>
Sent: Saturday, February 19, 2005 1:11 PM
Subject: [AVR-Chat] Motor Control Problems
>
> Hi,
>
> I am a 15 year old high school student using a tiny 26 on an odyssey
> of the mind project (we have a competition next week :) ). we are
> building a vehicle based on an 18 volt drill motor. i have built an H
> bridge based on the design on page 263 of "The Robot Builder's
> Bonanza". I am using BUZ11 n channel mosfets. I am also using a k2232
> (also a n channel mosfet) to drive the h bridge between ground and the
> rest of the H bridge. i am using diodes from source to drain. I am
> using PWM on the avr to control speed at just under 4 kHz and about a
> 40% duty cycle. everything works well in testing using a 7.2 V nicad
> and a small radio shack motor. when i try to connect to the drill
> motor and the 18V motor the cmos buffer i am using between the avr and
> the h bridge ( 74hc244e i think) smokes and has visible melting after
> the circuit works for a couple seconds. The drill motor draws just
> under 10 amps under load. i am going to try adding a capacitor
> tomorrow to reduce electrical noise but i was wondering if any one
> else has any suggestions for me?
>
>
> Thanks in advance for any suggestions
>
> Ben Matthews
> New York, USA
>
>
>
> Yahoo! Groups Links
>
> <*> To visit your group on the web, go to:
> http://groups.yahoo.com/group/AVR-Chat/
>
> <*> To unsubscribe from this group, send an email to:
> AVR-Chat-unsubscribe@yahoogroups.com
>
> <*> Your use of Yahoo! Groups is subject to:
> http://docs.yahoo.com/info/terms/
>
>
>
>
>
MSGTAG has notified the sender that you have read this message.