Re: How do I hook up my potentiometer?
- From: "Michael A. Terrell" <mike.terrell@xxxxxxxxxxxxx>
- Date: Fri, 29 Feb 2008 21:57:13 -0500
John Fields wrote:
On Mon, 18 Feb 2008 23:55:09 -0500, "Michael A. Terrell"
<mike.terrell@xxxxxxxxxxxxx> wrote:
John Fields wrote:
On Mon, 18 Feb 2008 20:24:12 GMT, ehsjr <ehsjr@xxxxxxxxxxxxxxxx>
wrote:
kayvee wrote:
I have a 500k ohm POT and I will be using it to vary the voltage of a
circuit I am making. It is basically a motor which I want to be able
to change the voltage drop across it. I will be connecting it in
series with the motor. This POT I have has 3 lead coming off of it. I
am under the impression that if I connect the middle lead and one of
the outer leads it will vary the current of the circuit, and if I
connect all 3 lead in a curtain fashion it will vary the voltage.
Now my question is how do I connect the 3 leads?
I have tried reading explanations, I would appreciate a straight
forward good old fashioned diagram.
[POT}
| | |
? ? ?
*---[DC]----?---------[MOTOR]---*
| |
| |
*-------------------------------*
Connecting a pot directly to a motor is not usually
advisable. As a general rule, assume that if you do
it, you will burn out the pot. If the motor draws
less current than the pot can handle, that's ok, but
you need to know that up front.
If you use a pot to drive a transistor, you can
control a lot more current:
V+ ---+----[Motor]----+
| |
P /c
O<---[220R]---| NPN Power xsistor
T \e
| |
Gnd ---+---------------+
The NPN transistor needs to be able to handle the
power and current that the motor needs.
---
V+ ---+---------------+
| |
P /c
O<------------| NPN Power xsistor
T \e
| |
Gnd --+---[Motor]-----+
Better, yes? :-)
Unless you turn the wiper all the way to the top terminal and destroy
the transistor. A resistor to limits the base current to a safe level
should be added between that terminal and V+. (For once I got to make
the correction before John caught it) ;-)
---
Since the circuit is an emitter follower, the voltage dropped across
the motor will cause the emitter voltage to rise as the base voltage
is increased, which will limit the base current to whatever's needed
to keep the base enough more positive than the emitter to allow more
and more current into the motor as the pot is rotated.
Still, it's not a bad idea and will allow Ed to maintain his
stranglehold on the world's supply of 220 ohm resistors. ;)
he better get busy. It lookks like I have over 10,000 on hand.
http://home.earthlink.net/~mike.terrell/Epres.html
Also, this may not be a bad idea:
.V+>---+---------------+
. | |
. [220] |
. | |
. P /c
. O<------------| NPN Power xsistor
. T \e
. | |
. +---[Motor]-----+
. | |
.GND>--+---[Diode>]----+
--
JF
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
.
- Follow-Ups:
- Re: How do I hook up my potentiometer?
- From: ehsjr
- Re: How do I hook up my potentiometer?
- Prev by Date: Re: Homemade DC to AC inverter questions
- Next by Date: Re: Dan Quayle Syndrome
- Previous by thread: Re: Loosening Sockets
- Next by thread: Re: How do I hook up my potentiometer?
- Index(es):
Relevant Pages
|
