Help with switches for simple circuit

[b-rad_76]

Hi,

**broken link removed**

I am trying to design a circuit to enable a push start button in my car.

It is easy enough to wire the push button to start the car (see my weird diagram) The problem is, the standard ignition switch disables pin 2 while it is at position 3.

With my setup the ignition switch is set to position 2 and then the momentary switch (purple) connects pin 4, 5 and 1 when depressed (as a substitute to position 3 on the ignition switch). But in turn, pin 2 is not disabled while the momentary switch is depressed.

Is there a way to disable pin 2 with the ignition switch at position 2 while the momentary switch is depressed?

PS FYI pin 2 is disabled while position 3 is activated to reduce current draw by accessories.

Thank you in advance,
Brad

 

[MrDEB]

I assume your using the key switch that came with car?
just turn key switch to run position and have a pushbutton going to the starter solenoid.
couldn't be easier.

 

[DirtyLude]

He's saying there is another connection which is deactivated when the starter is cranked (turns off accessories while the starter is running). He wants to keep that functionality with the starter button.

 

[TimK]

Not sure but could you use a NO momentary switch along with a relay with both NO and NC contacts. Connect the NO contacts to 1 and 4 5 and the NC contacts to 1 and 2.

That is if its ok to use a relay.

TimK

 

[Gary B]

You have to use a SPDT break before make switch. That way you can open pin 2 before closing pins 3, 4 and 5.

 

[Rajaneesh]

Hi,

**broken link removed**

I am trying to design a circuit to enable a push start button in my car.

It is easy enough to wire the push button to start the car (see my weird diagram) The problem is, the standard ignition switch disables pin 2 while it is at position 3.

With my setup the ignition switch is set to position 2 and then the momentary switch (purple) connects pin 4, 5 and 1 when depressed (as a substitute to position 3 on the ignition switch). But in turn, pin 2 is not disabled while the momentary switch is depressed.

Is there a way to disable pin 2 with the ignition switch at position 2 while the momentary switch is depressed?

PS FYI pin 2 is disabled while position 3 is activated to reduce current draw by accessories.

Thank you in advance,
Brad

Can you tell me the voltage levels in each pins while at position 2 ? So that i can give you a simple solution...

 

[b-rad_76]

Hi

Firstly thank you for all the input.

MrDEB - Yes this would be simple but as DirtyLude noted the accessory function is disabled whilst cranking

TimK - that sounds like a great idea, i was unaware that you could get such a relay, do you know if they are readily available, also would it be able to handle the some 15-40Amps that the ignition circuit can generate?

Gary B - I have limited knowledge in this area, so would you care to elaborate on your suggestion, thanks

Rajaneesh - although i have not tested this voltage, i believe it would be approx 12V as this is the voltage the accessory circuit functions on


Additionally, I was thinking that i could run a small gauge wire from after my momentary switch to a NC relay which be placed between pin 1 and 2 of position 2 of the ignition switch (pin 3 will still recieve power i believe) So that when i push the momentary switch the relay would open the connection to pin 2.. Thoughts?

Thank you,
Brad

 

[Rajaneesh]

Hi

Firstly thank you for all the input.

MrDEB - Yes this would be simple but as DirtyLude noted the accessory function is disabled whilst cranking

TimK - that sounds like a great idea, i was unaware that you could get such a relay, do you know if they are readily available, also would it be able to handle the some 15-40Amps that the ignition circuit can generate?

Gary B - I have limited knowledge in this area, so would you care to elaborate on your suggestion, thanks

Rajaneesh - although i have not tested this voltage, i believe it would be approx 12V as this is the voltage the accessory circuit functions on


Additionally, I was thinking that i could run a small gauge wire from after my momentary switch to a NC relay which be placed between pin 1 and 2 of position 2 of the ignition switch (pin 3 will still recieve power i believe) So that when i push the momentary switch the relay would open the connection to pin 2.. Thoughts?

Thank you,
Brad

Yes...this is what i was suppose to suggest...If you are getting 12v, you can put the 12V relay in the line and run the wires through the NC contact, so that it will get open when the relay is energised.... Check out the current drainage of this line before selecting the contact rating....

 

[Gary B]

Hi

Firstly thank you for all the input.

MrDEB - Yes this would be simple but as DirtyLude noted the accessory function is disabled whilst cranking

TimK - that sounds like a great idea, i was unaware that you could get such a relay, do you know if they are readily available, also would it be able to handle the some 15-40Amps that the ignition circuit can generate?

Gary B - I have limited knowledge in this area, so would you care to elaborate on your suggestion, thanks

Rajaneesh - although i have not tested this voltage, i believe it would be approx 12V as this is the voltage the accessory circuit functions on


Additionally, I was thinking that i could run a small gauge wire from after my momentary switch to a NC relay which be placed between pin 1 and 2 of position 2 of the ignition switch (pin 3 will still recieve power i believe) So that when i push the momentary switch the relay would open the connection to pin 2.. Thoughts?

Thank you,
Brad

SPDT is single poll double throw. It is a switch or in your case a push button with both a make and a break contact. You can find anything from little micro switches to chrome plated things large enough to etch “Push to Ignite” on the face.

 

[TimK]

Here is a link to one that may work. Also check at autoparts stores, I think some headlight relays may also work. They just need to be SPDT

Omron Electronic Components - G8JN-1C6T-DC12 - Allied Electronics

HTH
TimK

 

[TimK]

I could be wrong but I think using this relay you would connect
Pin1 to 30
Pin2 to 87a
Pin4 and 5 to 87
+12V to Push button switch
Push button switch to 85
-12V to 86

In it off state Pins 1 and 2 are connected
When the control voltage is applied (Push the Button) the relay is energized
Pin 1 is no longer connected to Pin 2
Pin 1 is now connected to Pins 4 and 5
When the button is released
Pins 4 and 5 are not connected to Pin 1
Pin 1 is connected to Pin 2

HTH