circuit design help: momentary switch activates/cancels electronic switch

[Fred Bloggs]

Okay, thanks for all the replies. Sorry to change things up on
you...but like I said early on, this is a learning experience for me.
It has occured to me that I don't want to worry about contact bounce
and that in reality, this will fit my application much better if there
are 2 momentary switches. pressing one of them turns the system on and
pressing the other turns the system off. i can probably adapt this
setup somehow from some of the provided circuits, so I will look into
it. this might actually simplify the circuit too i would think.

IF your load is inductive, non-resistive, or capacitive then something
like this would be better:
View in a fixed-width font such as Courier.

..
.. 12VDC>-------+----+---+-------+-----+-------+
.. | | | | | |
.. | | | | | 12VDC |
.. | | | | --RELAY---
.. | | | | |\ COM|
.. | [10K] | - |/ |
.. | | | ^ |\ |
.. | | | 1N4001 |/ NO |
.. | | | | ----------
.. >| | | | | |
.. 2N3906|--+---|-[10K]-+-----+ |
.. /| | | |
.. | o | |
.. | -| SWon | |
.. | o | +-------+
.. | | | | |
.. | | | - |
.. | | | ^ |
.. | [2.2K] | 1N4001 LAMP
.. | | | | |
.. | | ||- +-------+
.. +--------+-------+--||<IRF510 |
.. | | | ||- |
.. | o === | |
.. [10K] -| SWoff 0.01U | |
.. | o | | |
.. | | | | |
.. +--------+-------+-----+-------+
.. ---
.. ///

 

[Fred Bloggs]

Okay, thanks for all the replies. Sorry to change things up on
you...but like I said early on, this is a learning experience for me.
It has occured to me that I don't want to worry about contact bounce
and that in reality, this will fit my application much better if there
are 2 momentary switches. pressing one of them turns the system on and
pressing the other turns the system off. i can probably adapt this
setup somehow from some of the provided circuits, so I will look into
it. this might actually simplify the circuit too i would think.

IF your load is inductive, non-resistive, or capacitive then something
like this would be better:
View in a fixed-width font such as Courier.

.
. 12VDC>-------+----+---+-------+-----+-------+
. | | | | | |
. | | | | | 12VDC |
. | | | | --RELAY---
. | | | | |\ COM|
. | [10K] | - |/ |
. | | | ^ |\ |
. | | | 1N4001 |/ NO |
. | | | | ----------
. >| | | | | |
. 2N3906|--+---|-[10K]-+-----+ |
. /| | | |
. | o | |
. | -| SWon | |
. | o | +-------+
. | | | | |
. | | | - |
. | | | ^ |
. | [2.2K] | 1N4001 LAMP
. | | | | |
. | | ||- +-------+
. +--------+-------+--||<IRF510 |
. | | | ||- |
. | o === | |
. [10K] -| SWoff 0.01U | |
. | o | | |
. | | | | |
. +--------+-------+-----+-------+
. ---
. ///

Allowing for pressing both switches simultaneously, make this change:
View in a fixed-width font such as Courier.

..
.. 12VDC>-------+----+---+-------+-----+-------+
.. | | | | | |
.. | | | | | 12VDC |
.. | | | | --RELAY---
.. | | | | |\ COM|
.. | [10K] | - |/ |
.. | | | ^ |\ |
.. | | | 1N4001 |/ NO |
.. | | | | ----------
.. >| | | | | |
.. 2N3906|--+---|-[10K]-+-----+ |
.. /| | | |
.. | o | |
.. | -| SWon | |
.. | o | +-------+
.. | | | | |
.. +--------+ | - |
.. | | ^ |
.. | | 1N4001 LAMP
.. [1K] | | |
.. | ||- +-------+
.. +--------+-------+--||<IRF510 |
.. | | | ||- |
.. | o === | |
.. [10K] -| SWoff 0.01U | |
.. | o | | |
.. | | | | |
.. +--------+-------+-----+-------+
.. ---
.. ///

 

[John Fields]

Okay, thanks for all the replies. Sorry to change things up on
you...but like I said early on, this is a learning experience for me.
It has occured to me that I don't want to worry about contact bounce
and that in reality, this will fit my application much better if there
are 2 momentary switches. pressing one of them turns the system on and
pressing the other turns the system off. i can probably adapt this
setup somehow from some of the provided circuits, so I will look into
it. this might actually simplify the circuit too i would think.
THANKS!

---
This is the standard way to do it: (View in a fixed-pitch font like
Courier)


+V
|
S1| O +V
PRESS ON >--| |
| O---+ | O-------->NO
| |K1A O |K1B O--->COM
| +--> | +--> |
[COIL]- - -|- - - -|
|
S2 O|
PRESS OFF >-----|
O|
|
GND

S1 is a Single-Pole Single-Throw Normally Open (FORM 'A') momentary
switch which can handle the relay coil current, S2 is a Single-Pole
Single-Throw Normally Closed (FORM 'B') momentary switch which can
handle the relay current, and the relay is a DPSTNO or a DPDT relay.
One set of contacts is used to latch the relay in the energized
position when S1 is pressed, and the other set is used for external
purposes.

When S1 is pressed, current flows through the relay coil, which
attracts the armature of K1A to the normally-closed contact. When
they touch, another path to +V will be established for the coil,
latching the relay. S1 can then be released and the relay will
remain energized.

When S2 is pressed, the path to ground for the current will be
broken, the magnetic field around the relay coil will collapse, and
the contacts will spring back to their non-energized state.

 

[Rich Grise]

[op wrote:]

Okay, thanks for all the replies. Sorry to change things up on
you...but like I said early on, this is a learning experience for me.
It has occured to me that I don't want to worry about contact bounce
and that in reality, this will fit my application much better if there
are 2 momentary switches. pressing one of them turns the system on and
pressing the other turns the system off. i can probably adapt this
setup somehow from some of the provided circuits, so I will look into
it. this might actually simplify the circuit too i would think.

IF your load is inductive, non-resistive, or capacitive then something
like this would be better:
View in a fixed-width font such as Courier.

[circuits snipped]

Boy, that sure is a lot of stuff, when it could be done with an RS
flip-flop.

Cheers!
Rich

 

[John Fields]

Okay, thanks for all the replies. Sorry to change things up on
you...but like I said early on, this is a learning experience for me.
It has occured to me that I don't want to worry about contact bounce
and that in reality, this will fit my application much better if there
are 2 momentary switches. pressing one of them turns the system on and
pressing the other turns the system off. i can probably adapt this
setup somehow from some of the provided circuits, so I will look into
it. this might actually simplify the circuit too i would think.
THANKS!

---
This is the standard way to do it: (View in a fixed-pitch font like
Courier)


+V
|
S1| O +V
PRESS ON >--| |
| O---+ | O-------->NO
| |K1A O |K1B O--->COM
| +--> | +--> |
[COIL]- - -|- - - -|
|
S2 O|
PRESS OFF >-----|
O|
|
GND

S1 is a Single-Pole Single-Throw Normally Open (FORM 'A') momentary
switch which can handle the relay coil current, S2 is a Single-Pole
Single-Throw Normally Closed (FORM 'B') momentary switch which can
handle the relay current, and the relay is a DPSTNO or a DPDT relay.
One set of contacts is used to latch the relay in the energized
position when S1 is pressed, and the other set is used for external
purposes.

When S1 is pressed, current flows through the relay coil, which
attracts the armature of K1A to the normally-closed contact. When
they touch, another path to +V will be established for the coil,
latching the relay. S1 can then be released and the relay will
remain energized.

When S2 is pressed, the path to ground for the current will be
broken, the magnetic field around the relay coil will collapse, and
the contacts will spring back to their non-energized state.

---
For your lamp load:


+12V>-----------+--------+---------+
| | |
S1| O | |
PRESS ON >--| | |
| O---+ | |
| |K1A O |
| O--> | K1B O
[COIL]- - -|- - - - -|
| O--> |
S2 O| |
PRESS OFF >-----| [LAMP]
O| |
| |
GND>------------+-------------+

 

[Spehro Pefhany]

[op wrote:]
Okay, thanks for all the replies. Sorry to change things up on
you...but like I said early on, this is a learning experience for me.
It has occured to me that I don't want to worry about contact bounce
and that in reality, this will fit my application much better if there
are 2 momentary switches. pressing one of them turns the system on and
pressing the other turns the system off. i can probably adapt this
setup somehow from some of the provided circuits, so I will look into
it. this might actually simplify the circuit too i would think.

IF your load is inductive, non-resistive, or capacitive then something
like this would be better:
View in a fixed-width font such as Courier.

[circuits snipped]

Boy, that sure is a lot of stuff, when it could be done with an RS
flip-flop.

Cheers!
Rich

Does RS even sell chips any more?

;-)


Best regards,
Spehro Pefhany

 

[Rich Grise]

Fred Bloggs wrote:
[op wrote:]
Okay, thanks for all the replies. Sorry to change things up on
you...but like I said early on, this is a learning experience for me.
It has occured to me that I don't want to worry about contact bounce
and that in reality, this will fit my application much better if there
are 2 momentary switches. pressing one of them turns the system on and
pressing the other turns the system off. i can probably adapt this
setup somehow from some of the provided circuits, so I will look into
it. this might actually simplify the circuit too i would think.

IF your load is inductive, non-resistive, or capacitive then something
like this would be better:
View in a fixed-width font such as Courier.

[circuits snipped]

Boy, that sure is a lot of stuff, when it could be done with an RS
flip-flop.

Cheers!
Rich

Does RS even sell chips any more?

;-)

LOL!

But, just because I'm in a bluff-calling mood, yes:
http://support.radioshack.com/produ...6-2816&Name=High-Speed CMOS Logic ICs&Reuse=N
(mind the wrap)

Cheers!
Rich

 

[Fred Bloggs]

Does RS even sell chips any more?

;-)

Only the analog stuff, LM339, LM324, TL082, 555, 556, LM386, LM317,
7805, 7812, maybe some others, transistors, diodes, resistors, caps,
etc...but no digital IC's whatsoever available in the stores.

 

[matthewuw]

Terry Pinnel wrote: "Hey, how about an even simpler approach: a single
toggle switch?"

 

[Fred Bloggs]

Terry Pinnel wrote: "Hey, how about an even simpler approach: a single

toggle switch?"

A rocker switch would be best for light circuit control on a motorcycle.
These come in momentary also and can be controlled by thumb. One way
using readily available parts is shown below. When the rocker momentary
is moved to BATT position, voltage is applied through D1 to RLY1 and R1
to the transistor base turning both components on. D2 prevents load
current from flowing through the miniature switch. When RLY1 activates,
BATT is thrown onto the load ckt through the COM-NO contact closure, and
BATT is also applied through D2 to RLY1 and R2 to the TIP31 base drive.
SW1 can now be released and the circuit remains latched on. When SW1 is
moved to the GND position, junction of R1-R2 is pulled to GND removing
TIP31 base drive and turning it off. D1 prevents current flow from the
RLY1 NO ckt from flowing to GND. RLY1 cuts off, removing voltage from
the load and RLY1. The SW can now be released and the circuit remains
off. D3 suppresses RLY1 coil inductive flyback, and D4 kills transients
from the load wiring. R3 is a leakage drain resistor for the TIP31.

View in a fixed-width font such as Courier.

..
.. +---+ +-----------------------------+---->
.. | | | |
.. -+- | | | TO LAMP_CKT
.. /// | | +---->
.. GND | |
.. +-----------------------WTHR_PROOF_ENCL---+
.. | | | |
.. | +---------+ | |
.. | | | |
.. | | 1N4001 | 1N4001 |
.. | +-----|>|-----+---|>|---+ |
.. | | D4 | D2 | |
.. | | | +-----|--------+ | +---------+
.. | | | | | | | | |
.. | | ------- | | | | |
.. | | |NO COM| | | | | |
.. | | RLY1 | | | | | | SW MOM |
.. | | | | | | | | ROCKER |
.. | | | | | | | | +-----+ |
.. | | +--|-/\/\- |---+ | | | | | |
.. | | | ------ | +--|-------+ | o--|-+- BATT
.. | | TIP31 | D3 | 1N4001 | | / |
.. | +-E C--+---|>|--------+--|<|---+--|---------|--o |
.. | | B 1N4001 | D1 | | | \ |
.. | | | | | | | o--|---- GND
.. | [1K] | R1 R2 | | | | |
.. | |R3 | 120 120 | | | +-----+
.. | +---+----/\/\--+--/\/\--+ | | SW1
.. | 3W | 3W | |
.. | +-----------------+ |
.. | |
.. +-----------------------------------------+

 

[Rich Grise]

Terry Pinnel wrote: "Hey, how about an even simpler approach: a single
toggle switch?"

You might try one of these:
http://www.google.com/search?q=motorcycle+handlebar+switch

Good Luck!
Rich

 

[roma]

Here is the application:

I have a momentary switch. When I press it, I want to switch something
on (light bulb) and have it stay on even though momentary switch was
released. maybe 500 mA draw.

When I press it again, it turns the light bulb off. How do I do this?
This is in a 12VDC circuit.

Thanks!

http://members.shaw.ca/roma/switching.html , all kinds of electronic
switching for low volt/current applications .
roma