OK.. I need some N20 help.. It's a weird one..

[Super73]

Attached you will find a wiring diagram that I created for my set up. A few things about it.

2 stage NX kit.
2 arming switches, one for each stage.
Throttle switch
Fuel pressure safety switch
Single Window switch: Can not take a large ground (like noids) so I am using it to ground the coil of the relays.

I was testing it last night in the shop with it wired as shown minus the window switch. I didn't want to be reving the motor while my buddy tried listening to noids ect to see if things were working. The wire going from the Fuel Pressure Safety was left loose so I could simply ground it to the chassis as if it were through the window. Things weren't working right.

We found that some how there was a grounding issue and when arming the system (with the WS wire grounded) it was firing the noids with out the throttle switch being depressed. Double checked the throttle switch with a meter to make sure it was normally open and working right. All is fine with it. So we decided to disconnect the input of the throttle switch (ground from the relay coil 86). Flip the switches, still firing the noids.

We disconnected the 86 wire from relay and tested our circuit for a short to ground, IE through the throttle switch and through the fuel pressure safety switch. No short or ground.

The next thing we check were the arming switches since they go to ground for the LED or light in them. +12 in and Acc both are free of ground when off but both go to ground when on.

We disconnected the ground for the arming switches, and what do you know. Works perfect. Each stage will engage and release with the throttle switch, and both will as well if they are both armed.. They both work right with the window switch wire being manually grounded and ungrounded as if I was the switch..

I swapped (85) and (86) for the fun of it to see if any difference. No I didn't notice if it was doing this or not with them wired as the diagram but:

If the ground is hooked up to the arming switches, if 1 stage is armed alone with the WS wire grounded, the noids will not fire till WOT, but, they will not release if I lift or unground the WS. I have to turn the switch off. But if both stages are armed, they both will come on and off with the throttle assuming the WS wire is grounded.

Again, disconnecting the ground on the switches, works perfect.

So I'm hoping someone can tell me what would be causing this. I'm thinking I might just buy a couple nonlighted switches since I know it works right that way..

Would putting a diode on both (86)'s possibly fix the issue?

[hotrod 80]

Diodes will stop the feed back when 1 system is armed . There should be resistance through the switch lamps , not a direct path to ground . Also more details on the window switch . Is it single pole single through or a relay like your using above . Swapping the 85 and 86 should not change things . It is just a coil . Also NX has the 1st stage lock out . They say the lower bar is always first stage . Here's a link to there diagram . http://www.nitrousexpress.com/Instru...supplement.pdf

[Super73]

Didn't want to wire the way NX has it in the instructions as there are several safety things I'd like to implement.

I can't tell you a lot about the WS.. It's not a major production piece. There was a moderator of LS1tech years ago that was building them and selling them along with a 2 step and shift light. We all called him Harlan. Actully he is still making and selling them. http://www.harlan-engineering.com/store/store.html "Grounding output capable of sinking 0.5A of current" As mentioned, I knew a lot of current could not go through them.

Reason for swaping 85 and 86 is I know some relays use a built in diode. Figured it couldn't hurt..

I appreciate the input.

[Pyrotechnic]

In the situation where switch 1 is on and switch 2 is off, I think you are getting a path to ground through switch 2 when it's off.

Switch 1 sends current to the stage 1 relay, then through the ground wire to the stage 2 relay, then to switch 2, and then to the ground that switch 2 is providing.

I've included a simple schematic of they way I THINK your switches are wired. As you can see with the way the LED is positioned in the picture, the function of the light emitting diode WOULD allow a path back to ground in the off position.

You said you checked the switches for a path to ground, but a multimeter won't show you this. When I set my multimeter to measure resistance and I put the leads across a small LED I grabbed from my junk bin, the small LED actually lights up from the test current of the meter, but the resistance reads infinite.

The solution ? Get a pair of diodes and place them between the switches and the relays. This will prevent any path to ground through the LED's, and you get to keep your lighted switches.

[Super73]

Originally Posted by Pyrotechnic

In the situation where switch 1 is on and switch 2 is off, I think you are getting a path to ground through switch 2 when it's off.

Switch 1 sends current to the stage 1 relay, then through the ground wire to the stage 2 relay, then to switch 2, and then to the ground that switch 2 is providing.

The solution ? Get a pair of diodes and place them between the switches and the relays. This will prevent any path to ground through the LED's, and you get to keep your lighted switches.

I mentioned putting diodes in line of 85 on another site.. So My thinking is with you about power feed back, but shouldn't all grounds be broken when I break the circuit at the throttle switch when opened? I guess I could still see the power going to the switch 2 since it's acting as a ground source..

Originally Posted by Pyrotechnic

I've included a simple schematic of they way I THINK your switches are wired. As you can see with the way the LED is positioned in the picture, the function of the light emitting diode WOULD allow a path back to ground in the off position.

Little confused here.. Why wouldn't I want to put it inline so current passes through the diode to 85?

Originally Posted by Pyrotechnic

You said you checked the switches for a path to ground, but a multimeter won't show you this. When I set my multimeter to measure resistance and I put the leads across a small LED I grabbed from my junk bin, the small LED actually lights up from the test current of the meter, but the resistance reads infinite.

Did you take the time to wire this up and test it?? If so, thank you very much, that's more than a lot of people would do.. Even if you didn't, thank you for your input.. I'll be picking up 2 non lighted switches as well and 2 diodes today.. Would LED's work since they are a "light emitting diode"?

[Pyrotechnic]

Originally Posted by Super73

Little confused here.. Why wouldn't I want to put it inline so current passes through the diode to 85?

Hmm maybe I worded it funny. The solution IS to have the current from the switches to 85, pass through a diode.

Originally Posted by Super73

Did you take the time to wire this up and test it?? If so, thank you very much, that's more than a lot of people would do.. Even if you didn't, thank you for your input.. I'll be picking up 2 non lighted switches as well and 2 diodes today.. Would LED's work since they are a "light emitting diode"?

I just tested the LED theory with my meter, other than that drew out the circuit on a piece of paper and ran through it in my head.

You can keep your lighted switches.

Look at the diagram I made of the switch and imagine this. Current can only flow in the direction of that arrow on the diode. When the switch is on, you get current to the 12V+ switched terminal, current goes through the LED and it lights up, then to ground. Exactly how the switch should work.

Now imagine that the switch is OFF, but 12V+ is coming to, or feeding back to the 12V+ switched terminal on the switch. The effect is much like the last scenario, current is able to go through the LED to ground.

Make sense ? I'll try to clarify and give more example so you know whats happening here.

You can keep the lighted switches though. All this needs to work correctly is plain diodes on the wires to 85.

[Super73]

Something like this?

[Super73]

I could change it to this.. This is almost how NX says to do it.. Only changes is there is normally a push button between the Stage 2 switch and relay. Also the relays normally go to ground vs the window switch..

[Pyrotechnic]

Yes the way you added the diodes is right.

The NX way would work as well. The added benefit is that the second stage wont be on unless the first is. I suppose that's a good thing ? (I don't know much about nitrous).

It looks like you would still need the diodes with the NX way. They just moved the condition switches around and made stage 2 dependent on stage 1, but I still see a path back to ground if you have switch 1 on and switch 2 off.

[Super73]

Then I'll keep it the way I have it and add the diodes.. The thing I like about my way is I can run stage 1 or 2 or 1&2. This would allow me to jet stage 1 with a 100 hit, stage 2 with a 200 hit. If stage 1 hooks out of the hole, I can try stage 2 by itself out of the hole. If that works, then I can spray the extra 100 a little ways out. Then if stage 2 works out of the hole, I can try all 300 out of the hole with stages on..

[scatesracing]

Why not just put your w/s f/p f/t switches on the hot side instead of the ground.... not on the purge of course

[hotrod 80]

Originally Posted by Super73

Then I'll keep it the way I have it and add the diodes.. The thing I like about my way is I can run stage 1 or 2 or 1&2. This would allow me to jet stage 1 with a 100 hit, stage 2 with a 200 hit. If stage 1 hooks out of the hole, I can try stage 2 by itself out of the hole. If that works, then I can spray the extra 100 a little ways out. Then if stage 2 works out of the hole, I can try all 300 out of the hole with stages on..

Might double check NX website . the way i read it was lower bar must always be first stage . Sounds like your getting cose to having it fixed .

[Super73]

I can't put the W/S on the hot side. It is meant to ground the coil on the relays as it can only support .5a to ground..

[scatesracing]

Originally Posted by Super73

I can't put the W/S on the hot side. It is meant to ground the coil on the relays as it can only support .5a to ground..

So your telling me that there is more amps on the source side of the coil than on the ground side...

[scatesracing]

Originally Posted by scatesracing

So your telling me that there is more amps on the source side of the coil than on the ground side...


Actually, I was thinking you though inline with the noids.. But, I do "think" there is more current on the hot side of the coil than the ground side.. That's a good question to ask my Electrical Engineer friend..

A 30 amp automotive relay can be fired with as little as 140 milliamps ....At .5 amps you should have plenty to fire two of them. if you have iluminated toggles you may have to use two more relays to get you switches to light... I also put a relay on my trannybreak switch so nothing happens till I let go of that button.

[Super73]

So I have spoken to 2 of my EE friends.. If I understood right, the coild side of a relay has a V drop but the same A pull. This equates in less total W.. So I might take your advice and put the WS, FPSS and TPS on the incoming +12v side vs the ground..

[scatesracing]

What nx kit did you get... and by the way ifeel nx has the best tech support.they are great they will go out of their way to help. I had to call the nos guys one time about a jet size issue... nothing short of dick heads.. the nx guy gave me his cell number so he could help me while he was at the track himself..... cool guys.. just my two cents

[Pyrotechnic]

Glad things worked out with the diodes !

Originally Posted by Super73

So I have spoken to 2 of my EE friends.. If I understood right, the coild side of a relay has a V drop but the same A pull. This equates in less total W.. So I might take your advice and put the WS, FPSS and TPS on the incoming +12v side vs the ground..

The switches have none to very little resistance. Thus, they can be treated as piece of wire in the circuit. They will see the total power, voltage, and current of the entire circuit as calculated by ohm's law.

Furthermore, all the electrons that leave a voltage source must return. All those electrons that went through the positive side of the circuit, also flow through the negative side. The switches see the same amount of electrons, whether on the positive or negative side.

Doesn't matter where the switches are.

BUT, if that window switch uses some sort of integrated circuit chip that provides a path to ground when the condition is met, it has to be on the ground side. I don't know the schematic but this sounds like the case, especially given that maximum current rating. Though you could set up the window switch to trigger a relay, which would let the switch provide either a 12V+ signal or a ground, and would give it a very large current rating.

[Super73]

Right on.. I just got home and went to the shop with 2 diodes.. Wired them in line and it works like I wanted.. Thanks to all that participated in figuring out my issue.. It's nice to have other set of eyes looking at things..

Now I just need to add in the fuel pump switch side to both arming switches and the window switch on the intended ground. I should be able to start testing it for real in the next couple days..

One other thing I need to figure out is how much current pull all 4 noids take so I can put a fuse in line there..


I'm using the 2 stage plate system..