will this work?
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Joined: Jun 2001
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From: Charleston, SC
Car: 91 Camaro Vert
Engine: 02 LS1, HX40
Transmission: 2002 LS1 M6
will this work?
i have somthing that i want pulsed.... the speed of the pulse isnt really important, aslong as its getting a pulsing voltage.
being that a relay is a mechanical device, i would THINK that this setup i have will work...
has anyone done this before? will it work?
being that a relay is a mechanical device, i would THINK that this setup i have will work...
has anyone done this before? will it work?
Last edited by MrDude_1; Mar 15, 2004 at 01:16 PM.
Thread Starter
Supreme Member
Joined: Jun 2001
Posts: 9,550
Likes: 4
From: Charleston, SC
Car: 91 Camaro Vert
Engine: 02 LS1, HX40
Transmission: 2002 LS1 M6
Originally posted by Leroy
that would pulse so fast it would be almost a constand voltage not to mention annoying to no end
that would pulse so fast it would be almost a constand voltage not to mention annoying to no end
ok... lets say the load is a ignition coil.... of course the circuit has to break, just for a couple nanoseconds so that the coil can fire off a spark plug...
think that would work?
and yes, it would be extremly annoying. and the relay probly wont last long.... but as long as it lights off the plug, i dont mind..
afterall, i have a endless supply of free relays from the junkyard
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From: FL
The general idea will work, but your implementation will not really work. I have done this before for other reasons. A relay will burn out in a short time like this, but if a highly reliable relay is used the life span can be reasonable.
The way you need to do it is to use a double pole relay. Using the first set of contacts, connect the common to your +12V source. Connect the other side of the contacts to one side of your relay coil. Now connect the other side of the relay coil to ground. Place a capacitor across the relay coil with the plus side towards the contacts and the negative side towards the grounded side of the coil. The capacitor should have a minimum of a 25V rating. In my experience, you are going to want at least 47uF of capacitance. You will have to experiment with this.
Now use the other set of contacts as you see fit for your load.
To answers the whys, the capacitor is necessary to make the relay oscillation consistent. Otherwise, as soon as the relay breaks contact it is going to want to go back to the off position. This can, and will, create a large number of pulses that are extremely short. This causes a great deal of arcing inside of the relay and simply doesn't give the desired result.
To provide the relay coil with power after the relay contacts have opened a capacitor is added. The capacitor charges almost instantaneously when the relay contacts were closed. When the contacts open the capacitor begins discharging through the relay coil. When the voltage across the capacitor is below the relay's holding voltage the relay begins to close again. When it reaches the closed position, the cycle starts over. The larger the capacitor the more time it will keep the relay turned on.
I do not recommend using the same contacts to run the relay and the load. The ignition coil is going to generate a great deal of noise and voltage spikes. These stand a good chance of damaging the capacitor.
The way you need to do it is to use a double pole relay. Using the first set of contacts, connect the common to your +12V source. Connect the other side of the contacts to one side of your relay coil. Now connect the other side of the relay coil to ground. Place a capacitor across the relay coil with the plus side towards the contacts and the negative side towards the grounded side of the coil. The capacitor should have a minimum of a 25V rating. In my experience, you are going to want at least 47uF of capacitance. You will have to experiment with this.
Now use the other set of contacts as you see fit for your load.
To answers the whys, the capacitor is necessary to make the relay oscillation consistent. Otherwise, as soon as the relay breaks contact it is going to want to go back to the off position. This can, and will, create a large number of pulses that are extremely short. This causes a great deal of arcing inside of the relay and simply doesn't give the desired result.
To provide the relay coil with power after the relay contacts have opened a capacitor is added. The capacitor charges almost instantaneously when the relay contacts were closed. When the contacts open the capacitor begins discharging through the relay coil. When the voltage across the capacitor is below the relay's holding voltage the relay begins to close again. When it reaches the closed position, the cycle starts over. The larger the capacitor the more time it will keep the relay turned on.
I do not recommend using the same contacts to run the relay and the load. The ignition coil is going to generate a great deal of noise and voltage spikes. These stand a good chance of damaging the capacitor.
Thread Starter
Supreme Member
Joined: Jun 2001
Posts: 9,550
Likes: 4
From: Charleston, SC
Car: 91 Camaro Vert
Engine: 02 LS1, HX40
Transmission: 2002 LS1 M6
Originally posted by Dr. Pepper
The general idea will work, but your implementation will not really work. I have done this before for other reasons. A relay will burn out in a short time like this, but if a highly reliable relay is used the life span can be reasonable.
The way you need to do it is to use a double pole relay. Using the first set of contacts, connect the common to your +12V source. Connect the other side of the contacts to one side of your relay coil. Now connect the other side of the relay coil to ground. Place a capacitor across the relay coil with the plus side towards the contacts and the negative side towards the grounded side of the coil. The capacitor should have a minimum of a 25V rating. In my experience, you are going to want at least 47uF of capacitance. You will have to experiment with this.
Now use the other set of contacts as you see fit for your load.
To answers the whys, the capacitor is necessary to make the relay oscillation consistent. Otherwise, as soon as the relay breaks contact it is going to want to go back to the off position. This can, and will, create a large number of pulses that are extremely short. This causes a great deal of arcing inside of the relay and simply doesn't give the desired result.
To provide the relay coil with power after the relay contacts have opened a capacitor is added. The capacitor charges almost instantaneously when the relay contacts were closed. When the contacts open the capacitor begins discharging through the relay coil. When the voltage across the capacitor is below the relay's holding voltage the relay begins to close again. When it reaches the closed position, the cycle starts over. The larger the capacitor the more time it will keep the relay turned on.
I do not recommend using the same contacts to run the relay and the load. The ignition coil is going to generate a great deal of noise and voltage spikes. These stand a good chance of damaging the capacitor.
The general idea will work, but your implementation will not really work. I have done this before for other reasons. A relay will burn out in a short time like this, but if a highly reliable relay is used the life span can be reasonable.
The way you need to do it is to use a double pole relay. Using the first set of contacts, connect the common to your +12V source. Connect the other side of the contacts to one side of your relay coil. Now connect the other side of the relay coil to ground. Place a capacitor across the relay coil with the plus side towards the contacts and the negative side towards the grounded side of the coil. The capacitor should have a minimum of a 25V rating. In my experience, you are going to want at least 47uF of capacitance. You will have to experiment with this.
Now use the other set of contacts as you see fit for your load.
To answers the whys, the capacitor is necessary to make the relay oscillation consistent. Otherwise, as soon as the relay breaks contact it is going to want to go back to the off position. This can, and will, create a large number of pulses that are extremely short. This causes a great deal of arcing inside of the relay and simply doesn't give the desired result.
To provide the relay coil with power after the relay contacts have opened a capacitor is added. The capacitor charges almost instantaneously when the relay contacts were closed. When the contacts open the capacitor begins discharging through the relay coil. When the voltage across the capacitor is below the relay's holding voltage the relay begins to close again. When it reaches the closed position, the cycle starts over. The larger the capacitor the more time it will keep the relay turned on.
I do not recommend using the same contacts to run the relay and the load. The ignition coil is going to generate a great deal of noise and voltage spikes. These stand a good chance of damaging the capacitor.
that sounds better.... i think i'll try that... thanks
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