Water injection and racing & more

[Raymond C Drouillard]

On Sun, 10 May 1998 15:23:20 -0500 Walter Petermann
<corsaro at brokersys.com> writes:
>Matthew Harding wrote:
>>  .......
>> I need something that will accept an input voltage between 0 and 5
V... and a clock pulse
>> and depending on the input voltage, output a pulse who's width varies
linearly...
>> have i explained this right
>> so say there's a clock pulse, and the input voltage is 0V, I want a
puls of
>> 2ms to be the output....
>> if there;s a clock pulse, and the input voltage is 5V, I want a pulse
of
>> 6ms to be output....
>> 
>> 5V                                     *
>>                                     *
>> 4V                               *
>>                               *
>> 3V                         *
>>                         *
>> 2V                   *
>>                   *
>> 1V             *
>>             *
>> 0V       *
>> 
>>         2ms     3ms     4ms     5ms     6ms
>> 
>> bit like that.....
>> 
>> can anyone help me?  I do not want to use any microprocessors in the
>> design....
>> 
>> thanks
>
>Mathew,
>If you are handy with electronics you could try a timer chip
>like Motorola MC1455/1555. This has a trigger input (for
>your clock) and a threshold input to which you would connect
>your variable voltage. The output can sink up to 200ma,
>enough to turn on an automotive relay (about 80 ohm coil)
>with a supply of 12v. Although it would be best to use an
>external transistor for the relay. 
>
> Walter

Another method uses a sawtooth or triangle wave generater and a
compariter.  Feed the sawtooth into one of the compariter inputs, and the
reference voltage (perhapes amplified and level-changed with a couple of
op-amps) into the other input.  As the reference voltage goes up, the
amount of time that the sawtooth voltage is below the reference will
increase and the pulse will widen.

To modify this scheme for your purposes, use the pulse to trigger the
charging (or discharging) of a capaciter with a constant current source
(a JFET will work well).  This will produce a linear ramp.  A little
fiddling with the resisters and you'll have what you need.

Ray Drouillard

_____________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com
Or call Juno at (800) 654-JUNO [654-5866]