Simple circuit help

D

dave s

Guest
I essentially know next to nothing in the electronics field so could
do with a little help.

I have a microchip pic processor installed in a simple circuit
(SIMMSTICK) and need to use it to switch an external power circuit
on/off. I'm guessing I need to use a relay to do this (assuming I've
correctly guessed the function of a relay) but have no idea how to how
to hook this up to the PIC nor which type of relay I should be using.

The external circuit is 1..14V/1A DC . The control circuit operates at
5V DC.

Could anyone point me in the right direction?

Thanks
Dave
 
Hi Dave,

There is a lot you don't say. Can you program? Is somebody going to do the
wiring for you? O.K. Whatever.

A PIC can control a FET and this can control a relay. Or the FET can also
directly control an external circuit.

Use an N-Channel FET (maybe an STD12NE06) for common ground, the output will
need a pull-up. Simple, yes.

Jay

--
..
----------------------------------------------------------------------------
"I'm pullin' for you; we're all in this together", Red Green
----------------------------------------------------------------------------
..
..
"dave s" <spam@127.0.0.1> wrote in message
news:eek:6hmovoickkkc3ct7qlbj7qj7mebeh4j7o@4ax.com...
I essentially know next to nothing in the electronics field so could
do with a little help.

I have a microchip pic processor installed in a simple circuit
(SIMMSTICK) and need to use it to switch an external power circuit
on/off. I'm guessing I need to use a relay to do this (assuming I've
correctly guessed the function of a relay) but have no idea how to how
to hook this up to the PIC nor which type of relay I should be using.

The external circuit is 1..14V/1A DC . The control circuit operates at
5V DC.

Could anyone point me in the right direction?

Thanks
Dave
Click to expand...
 
On Mon, 13 Oct 2003 21:46:52 -0400, "happyhobit"
<happyhobit@wideopenwest.com> wrote:

Hi Dave,

There is a lot you don't say. Can you program? Is somebody going to do the
wiring for you? O.K. Whatever.
Click to expand...
I can program & solder, the problem is that my electronics knowledge
goes no further than what I was taught in school at 15 (as a minor
part of a physics class).


A PIC can control a FET and this can control a relay. Or the FET can also
directly control an external circuit.

Use an N-Channel FET (maybe an STD12NE06) for common ground, the output will
need a pull-up. Simple, yes.
Click to expand...
By common ground do you mean common to both the external & control
circuit? If so I'm not sure this is doable - the external power
circuit is a battery charger with it's own psu.
 
Dave, if you post me direct, with a valid e-mail address, I'll post you a
circuit. I can't post a JPG to this group.

Jay


--
..
----------------------------------------------------------------------------
"I'm pullin' for you; we're all in this together", Red Green
----------------------------------------------------------------------------
..
..
"dave s" <spam@127.0.0.1> wrote in message
news:84mmovkc6u01hbooqt0vpr6fao1t9fevda@4ax.com...
On Mon, 13 Oct 2003 21:46:52 -0400, "happyhobit"
happyhobit@wideopenwest.com> wrote:

Hi Dave,

There is a lot you don't say. Can you program? Is somebody going to do
the
wiring for you? O.K. Whatever.


I can program & solder, the problem is that my electronics knowledge
goes no further than what I was taught in school at 15 (as a minor
part of a physics class).


A PIC can control a FET and this can control a relay. Or the FET can also
directly control an external circuit.

Use an N-Channel FET (maybe an STD12NE06) for common ground, the output
will
need a pull-up. Simple, yes.

By common ground do you mean common to both the external & control
circuit? If so I'm not sure this is doable - the external power
circuit is a battery charger with it's own psu.
Click to expand...
 
On Tue, 14 Oct 2003 03:10:03 +0100, dave s <spam@127.0.0.1> wrote:

On Mon, 13 Oct 2003 21:46:52 -0400, "happyhobit"
happyhobit@wideopenwest.com> wrote:

Hi Dave,

There is a lot you don't say. Can you program? Is somebody going to do the
wiring for you? O.K. Whatever.


I can program & solder, the problem is that my electronics knowledge
goes no further than what I was taught in school at 15 (as a minor
part of a physics class).
Click to expand...
You might get some ideas here:
http://www.chipcenter.com/circuitcellar/september99/c99cd5.htm
or elsewhere around the Circuit Cellar site.

--
Rich Webb Norfolk, VA
 
I have a microchip pic processor installed in a simple circuit
(SIMMSTICK) and need to use it to switch an external power circuit
on/off. I'm guessing I need to use a relay to do this (assuming I've
correctly guessed the function of a relay) but have no idea how to how
to hook this up to the PIC nor which type of relay I should be using.

The external circuit is 1..14V/1A DC . The control circuit operates at
5V DC.

Could anyone point me in the right direction?

Thanks
Dave
Click to expand...
Try this (view with fixed font like M$ Notepad)...

VCC (5VDC)

|
|
.----o
| | 5V Coil
1N4002 - _|_ Relay
^ |_/_|-
| |
| |
|----o
|
|
6.8K |
___ |/
o------|___|---o-------| 2N3904
PIC Output | |>
.-. |
| | |
6.8K | | |
'-' |
| |
GND GND

created by Andy´s ASCII-Circuit v1.22.310103 Beta www.tech-chat.de

Try to get a small relay with a 5V coil that has a coil resistance of greater
than 50 ohms. Connect your external circuit to the contacts of the relay coil.
If your external circuit is an inductive load, you may have to put a snubber
across the load to prevent arcing at the relay contacts from upsetting your
micro. Try sci.electronics.basics next time.

Good luck.
Chris
 
Try sci.electronics.basics next time.
Click to expand...
Oops. Sorry -- it's getting a little late. Thought this was S.E.D. until .083
sec. after posting.

Good luck.
Chris
 
On 14 Oct 2003 04:01:14 GMT, cfoley1064@aol.com (CFoley1064) wrote:

Try sci.electronics.basics next time.

Oops. Sorry -- it's getting a little late. Thought this was S.E.D. until .083
sec. after posting.
Click to expand...
No problem :), it's late here also. Thanks for the circuit. Just one
quick question re: the snubber - I'm assuming this is also known as a
contact suppressor (I did say I know next to nothing about
electronics), does this go across the load or the relay contacts & is
there an optimum farad/ohm rating I should be looking for?

THX
dave
 
Just one
quick question re: the snubber - I'm assuming this is also known as a
contact suppressor (I did say I know next to nothing about
electronics), does this go across the load or the relay contacts & is
there an optimum farad/ohm rating I should be looking for?

THX
dave
Click to expand...
It really depends on the type of load you're switching with the relay. If
you're turning ON/OFF a DC inductive load, you can put a diode across it just
like the one across the relay coil in the diagram. Just use a diode rated for
at least twice the current that normally goes thru the load, and at least twice
the voltage that's across the relay when it's off. I'm reading either 1 to 14
VDC, 114VDC, or 1.14VDC at 1A on your first post. Without knowing what you're
switching it's pretty much guesswork, but you might want to try putting a
1N5403 across your load (cathode on the positive side, of course). It's a safe
bet.

Good luck.
Chris
 
On 14 Oct 2003 12:32:32 GMT, cfoley1064@aol.com (CFoley1064) wrote:

Just one
quick question re: the snubber - I'm assuming this is also known as a
contact suppressor (I did say I know next to nothing about
electronics), does this go across the load or the relay contacts & is
there an optimum farad/ohm rating I should be looking for?

THX
dave

It really depends on the type of load you're switching with the relay. If
you're turning ON/OFF a DC inductive load, you can put a diode across it just
like the one across the relay coil in the diagram. Just use a diode rated for
at least twice the current that normally goes thru the load, and at least twice
the voltage that's across the relay when it's off. I'm reading either 1 to 14
VDC, 114VDC, or 1.14VDC at 1A on your first post. Without knowing what you're
switching it's pretty much guesswork, but you might want to try putting a
1N5403 across your load (cathode on the positive side, of course). It's a safe
bet.
Click to expand...

Thanks Chris, the relay is to be used as a simple ON/OFF switch & the
VDC is 1 to 14, sorry for the confusion.

I couldn't find 1N5403s in my suppliers catalog but did find 1N5401s
which seem to fit in with your description above.

Many thanks for the help.
dave
 
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