VERY simple dc motor drive circuit?



Either an OpAmp with enough power capability to run the motor directly, or an OpAmp with a boost transistor added at the output.

Yes.
No, VC is the "command"

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
[....]

Don't forget the diode on the motor to eat the spike as the MOSFET turns off.
If you run the pin 5 of the 555 to a zener, you can compensate for the variations in the input voltage.
--
--
snipped-for-privacy@rahul.net forging knowledge


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
John E. wrote:

Put an emittor follower behind the potentiometer.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You want one part called a rheostat. Assuming the motor near full load at 500 mA then the resistance will be E/I = 10 ohms. Filament control rheostats were often zero to 25 ohms at around 5 watts. Odds are you will end up using a 10 ohm resistor. If thats not enough, try 20 ohms or so.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

wart
feedback,
http://www.uoguelph.ca/~antoon/circ/pwm555.html
JT

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

LM317, a pot, & a couple of resistors should do the trick easily & cheaply. Suitable circuits can be found on most LM317 data sheets.
--
W "Some people are alive only because it is illegal to kill them."
. | ,. w ,
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That's not good. Every problem must be solved by a circuit using either an LM555 or a PIC, perferably both :>
Earlier, I suggested the LT1083 as a better way to go than the LM317 because of the heat issue. I have also thought of a very ugly circuit like this:
Input +V ------+------------------+----------------+----- To motor ! ! ! ! \ ! ! / --- ! -- \ --------- ^ ! ! ! ! ! ! --- +---/\/\---++----+----- To motor ! --- ! ! \ ! !/e ! / <----/\/\--+---! PNP ! \ !\ !/ ! +---------! NPN ! ! !\e \ \ ! / / GND \ \ ! ! GND GND
This requires much less current in the POT than the single transistor one. The NPN's heat is a lot lower too.
--
--
snipped-for-privacy@rahul.net forging knowledge


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 4 Mar 2007 18:09:11 +0000 (UTC), snipped-for-privacy@green.rahul.net (Ken Smith) wrote:

Hey, LM317s are /nearly/ as traditional an answer to any kind of electronics problem as the classic 555, & much more traditional than those new-fangled PICs. ;) (And my science teacher in highschool used LM3909 as his solution for most things.)
--
W "Some people are alive only because it is illegal to kill them."
. | ,. w ,
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Take a look at the links here http://www.epanorama.net/links/motorcontrol.html#dc
--
Tomi Engdahl (http://www.iki.fi/then /)
Take a look at my electronics web links and documents at
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.