splitting voltage

[ehsjr]

Here's a simple PWM circuit to control your motor:

View in fixed font:

+6 ---+------------------------------------------+
a| |
[D1] |
| |
+------+----+---------+ +-----+
| | | | | |
| [1K] | ---------- [D3] [Motor]
| | | | 8 | a| |
| | +----|4 | | |
| / | | +-----+
| 25K \<---+----|7 555 | |
| / | | | /
| | a| | 3|---[100R]---| TIP31
| [1K] [D2] | | \ e
| | | | | |
| +----+----|6 | |
| | | | | |
| | +----|2 5|----+ | Diodes: 1N4001
| + | | | | | banded end is
[C1] [C2] ---------- [C3] | cathode; anode
|1000 | .1uF | .01uF | end marked with
| uF | | | a on this
Gnd --+------+-------------------------+---------+ drawing

There are more complicated PWM circuits, but this
simple one should do what you need.
Parts: 2 1K resistors, 1 100 ohm resistor
1 25K potientiometer,
1 1000 uF 16 volt electrolytic capacitor,
1 .1 uF capacitor, 1 .01 uF capacitor
3 1N4001 diodes, 1 555 timer, 1 TIP31 transistor

Build this circuit and connect it to the 6 V battery
source by itself. Be sure to observe the polarity of
the diodes and C1. Test it to make sure you can get
the correct flow rate from the pump. Once you have
it set up properly, then you can connect your the
other 555/transistor/LED circuit. Don't forget to
add the recommended capacitor & diode to your
555/transistor/LED circuit, per the diagram John Fields
provided. They are already added to the PWM circuit
in this post.

Ed

This is the same circuit as I linked to in my previous post, minus the
voltage protection. Am I correct? If so, I'm glad I'm on the right
track Thanks again for your help!

-sam

Close - it is a similar circuit. The one I posted is
adjustable, the one at the Doctronics site is not.

Ed