# Help needed for 5 button selector circuit

G

#### Glenn Ashmore

Jan 1, 1970
0
I have a bank of 5 DPDT momentary push button switches like the kind used
for preset frequencies on a car radio. I need a circuit with 5 outputs to
drive some relays such that when a button is pushed it latches the
corresponding output high and turns the other 4 off. This has got to be
fairly simple but I just can't figure out how to do it. Any suggestions?

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com

J

#### Jamie

Jan 1, 1970
0
Glenn said:
I have a bank of 5 DPDT momentary push button switches like the kind used
for preset frequencies on a car radio. I need a circuit with 5 outputs to
drive some relays such that when a button is pushed it latches the
corresponding output high and turns the other 4 off. This has got to be
fairly simple but I just can't figure out how to do it. Any suggestions?
yes, with that kind of switch you can do it.
on each switch you need to use the NC (normally close) contact on one side
to maintain a constant voltage to all relays on one of the NO (normally
open contact).
So each Relay needs to be a DP, one pole for your use and the other
for the Loop lock to keep the relay in.
All the switches will be wired in series using this NC contact so that
when ever you press one, it will open the circuit at the end of the
string which is supplying the lock voltage on the contacts.

So just picture the lock voltage being connected to each (NO) contact
of each relay in parallel.
on the other side of the (NO) of each relay, you will connect one side
of it's own coil. This is where Coil will be getting it's energized
voltage from to hold it on. the other Coil connection will just be tied
to common along with the rest of the relays.
-- Now for the activation of the relay you want --

When you press a button, the (NC) contacts on the switch that is in
series with the rest of the (NC) contacts of the other switches will
open. this will cause loss of voltage in the remaining string of (NC)
contacts and which ever relay that was locked on will now release.
With the (NO) normally open contact of each switch, you will supply
to each coil power on the coil side connection of the relay..
remember i said the coil will be connected to the opposite side of
the locking contacts on each relay? this is where you connect your
momentary source to pull in the relay. when the relay pulls in, the
locking contacts will maintain it and with the mechanical slowness
of the relay returning, you should be able to release the button quick
enough to have it put the locking source back on before the relay pulls
open.
If you find that the relay pulls back to soon? You can then use a
Cap on the output of each switch that energizes the relay coil going
to common to hold a charge. use a diode in series after that to feed
the relay coil.
The diode is to prevent the cap from being charged while the relay
is locked on so that it releases quickly, and only be charged from the
switch..
I don't have a ASCII translation program to use here otherwise, i would
have drawn it out for you.

personally, i would use Flip Flops with RESET and SET (RS) type.
The (NC) would force a Reset of all flip-flops with their RESETS tied
together, and the closer and opening of the NO contacts would be tied to
each Flip-flop's SET pin.
The Q outputs would reflect the state.
The RESET and SET pins need to be pull low to high to activate.
you would need small cap on the reset line to prevent debouncing.

C

#### Chris

Jan 1, 1970
0
I have a bank of 5 DPDT momentary push button switches like the kind used
for preset frequencies on a car radio. I need a circuit with 5 outputs to
drive some relays such that when a button is pushed it latches the
corresponding output high and turns the other 4 off. This has got to be
fairly simple but I just can't figure out how to do it. Any suggestions?

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com

Hi, Glenn. You want simple? Here's simple. Get a 12VDC supply, some
5VDC coil DPDT relays, and 5 resistors R that have a resistance about
1.2 times the coil resistance of the relays, and can handle the
wattage when 12VDC is applied. Go to your junkbox and dig up 25
diodes, and make 5 of these (view in fixed font or M\$ Notepad):

| VCC
| +
| |
| .-.
| R1| |
| | |
| '-'
| |
| o--< From SW2
| |
| o--< From SW3
| |
| o--< From SW4
| |
| o--< From SW5
| |
| .----o
| D| RY1|
| - C| D
| ^ C| .--|<--<To RY2/R2
| | C| | D
| | | o--|<--<To RY3/R3
| '----o | D
| | o--|<--<To RY4/R4
| | | D
| .---------o o--|<--<To RY5/R5
| | | |
|CRY 1A| SW1 | o | o
| ----- |=|> - - |>
| ----- | o | o
| | | |
| | | |
| | | |
| === === ===
| GND GND GND
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

When making this, SW1 and RY1 stand for the relay associated with the
switch you're working on, and 2 through 5 stand for the others. The
second set of relay contacts on the relays are your outputs. The idea
is that pressing the DPST button performs two functions. First, it
energizes the coil of the relay (and the first relay contact latches
it in). Then, the other part of the switch momentarily shorts out the
other four relays, opening all of them.

extra current when a button is pressed to pay for the simplicity. But
it's pretty much foolproof, and behaves when more than one button is
pressed (all relays off if more than one button is pressed). Make
sure your radio buttons can handle the current of the 5 resistors.

Hope this does the job.

Cheers
Chris

G

#### Glenn Ashmore

Jan 1, 1970
0
Thanks! Both of those are great ideas! I was trying to think digital but
good old hard wiring works.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com

E

#### ehsjr

Jan 1, 1970
0
Glenn said:
I have a bank of 5 DPDT momentary push button switches like the kind used
for preset frequencies on a car radio. I need a circuit with 5 outputs to
drive some relays such that when a button is pushed it latches the
corresponding output high and turns the other 4 off. This has got to be
fairly simple but I just can't figure out how to do it. Any suggestions?

This will do it, and you can use simple SPST momentary
pushbuttons.

PNP
+12 -+--. .------[1K]----+----+----+----+---{{{-+----+
| e\ /c | | | | | |
| --- [D6][RLY] [D7][RLY] [D10][RLY]
| | |a | |a | |a |
| | +----+ +----+ +----+
| | | | |
| | [SCR1] [SCR2] [SCR5]
| | Pb1 /| /| /|
| | ___ | | | | | |
----------+--o o---[10K]--+ +---------+---{{{------+--+
| | | | | |
| | +--->|-------+ | | |
| | D1 | | | |
| | Pb2 | | | |
| | ___ | | | |
| +--o o---[10K]------------+ | |
| | | | | |
| | +--->|-------+ | |
| | D2 | | |
| {{{ {{{ | |
| | Pb5 | | |
| | ___ | | |
| +--o o---[10K]------------------{{{----+ |
\ / | | |
D11 --- +--->|-------+ |
| D5 | |
| | |
------+---[.1uF]------+ |
| | |
[1K] [10K] |
| | |
Gnd --------------+---------------+-------------------------+

For SCRs you can use 511-X00602MA2AL2 from Mouser, (18 cents
each) or anything else that will turn on at relatively low
current, with a hold current of ~ 10 mA. Diodes are 1N4148 or
whatever you have, and the PNP can be just about any common
jelly bean part, like a 2N3906.

_How it works_
The PNP is biased on by the 1K and D11, until a + pulse through
the .1 uF cap biases it off, briefly. That causes any SCR that
is on to turn off. The + pulse occurs when any button is pressed.
Whichever button is pressed gates the corresponding SCR on, which
energizes the corresponding relay. The SCR stays on until the next
time a button is pressed.

Ed

J

#### jasen

Jan 1, 1970
0
I have a bank of 5 DPDT momentary push button switches like the kind used
for preset frequencies on a car radio. I need a circuit with 5 outputs to
drive some relays such that when a button is pushed it latches the
corresponding output high and turns the other 4 off. This has got to be
fairly simple but I just can't figure out how to do it. Any suggestions?

one set of NC switch contacts is used to cut the holding power of the other
relays

shown is relay m of n

___ ___
| | _-v .--->ONm
+V --o | o...o | o--->>-----~: | ---
--+-- --+-- Vsus : ^---+-->|-.D2 |
S1a Sna : | --+--
|~|---+------+-------o o---< +V
|\| -|<-. D1 Smb
|_|--------+--< 0V
RLYm

Vsus is derived from one set of normally closed switch contacts
on each button all wired in series this same signal goes to all
the relays.

D1 eats inductive spikes, D2 protects against the case where all the
buttons are depressed at the same time.

A capacitor may be needed in parallel with D1 - it depends how fast the
relays and buttons are

note that the load current passes through all the switches,
if that's bad use a DPST relay (or better) like this:

high power version
_-v
+V>-----~:
___ ___ : ^--->ONm
| | _-v
+V --o | o...o | o--->>-----~: ---
--+-- --+-- Vsus : ^------>|-.D2 |
S1a Sna : | --+--
N/C |~|---+------+-------o o---< +V
|\| -|<-. D1 Smb
|_|--------+--< 0V N/O
RLYm

Bye.
Jasen

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