Coil relay mod with a twist

[posplayr]

Salty

Salty

If the original problem still exists it's still not an issue.

As I stated above connect 30 to 87 in the relay socket & you basically hot wire the battery directly to the coils. It will be like having the relay latched permanently.

That will get you home or to a store for a new relay, just remember to break the connection whenever you stop or you will burn out your coils....

As you can see, it really is a true failsafe to carry a jumper cable.

Dan

I guess I missed the fact you were hot wiring. OK I guess if you need to get home and it is that or nothing. I would still carry the spare relay and resort to the hot wire as a means of last resort. And replace with a relay ASAP. Or remove the jumper if you stop for any amount of time (more that 2-3 minutes).

My first inclination would have been to jumper the control wire back to the coils and live with the voltage drop. Yes you would suffer the original problem, but you are back to stock function.

I assume you mounted your relay on the flexible metal extension to reduce shock and vibe to the relay. Wanted to bring that out in case others did not realize that.

Pos

 

[salty_monk]

Yes, that & the fact that I needed some kind of bracket to make it fit there whilst still allowing the plastic cover with tool case pocket thing to drop back in

 

[MrZig]

I still don't understand why my original question won't work.

Posplayr, you said that if I do it my way, the relay won't ever work again? Why?

Sure, you'd have 10.5 volts going to 87, but it makes no difference what side the positive is on, whether its 87 or 30. The only thing that controls whether or not the relay will latch is 85 and 86. Neither one of these has any contact with those and shouldn't cause a latching issue.

Maybe you could explain it differently?

 

[posplayr]

MrZig

MrZig

The output is tied to the input and so the input can't drop again.

I'm assuming you plan to connect the output of your ignition switch/left hand ON switch (Orange / White) wire to control the relay at say 85 with 86 to GND.

You stated you would leave the stock wiring in place (i.e. the Orange / White) connected to the coils +. Since you are also connecting the Normally open 87 to the ignition coils positive , then you have connected indirectly (in the harness) the 85 to 87.

When you close the start button, 85 goes to +10.5 energizes the relay coil and pulls 87 to +12V. Since there is nothing to actively pull down 85(+12V stays on 85), when you open the ignition switch , 85 stays high because it is being pulled up by 87 and 87 stays high because 85 high(i.e. latch up at +12V). You have to disconnect the battery to have the relay go back to the open state.


The solution to this is to isolate the current flow between 85 and 87 by allowing current to only from from 85 to 87 and not back. The diode performs this function but with a forward drop so now you are at 9.7V instead on 10.5V.

Pos

 

[reddirtrider]

I still don't understand why my original question won't work.

Posplayr, you said that if I do it my way, the relay won't ever work again? Why?

Sure, you'd have 10.5 volts going to 87, but it makes no difference what side the positive is on, whether its 87 or 30. The only thing that controls whether or not the relay will latch is 85 and 86. Neither one of these has any contact with those and shouldn't cause a latching issue.

Maybe you could explain it differently?

Let me give it a shot. I'm not Pos, but I am a practicing EE and understand what he said.

Let's start at a point prior to starting your bike. With 86 and 87 shorted together you have power applied to the coils, even with the relay open. Now, you turn on the ignition and the relay closes. At this point you have 2 paths for the current to the coils (the short from 86 to 87 and the closed relay 30 to 87). Still no problem with the bike running.

Now it's time to turn off your bike. You remove the normal path for current to 86, but since you have 86 connected to 87 by a short, and the relay is still closed, power is still applied to the 86, through the relay, and it remains closed (until your battery dies).

Mock it up and give it a try.

 

[reddirtrider]

I'm assuming you plan to connect the output of your ignition switch/left hand ON switch (Orange / White) wire to control the relay at say 85 with 86 to GND.

You stated you would leave the stock wiring in place (i.e. the Orange / White) connected to the coils +. Since you are also connecting the Normally open 87 to the ignition coils positive , then you have connected indirectly (in the harness) the 85 to 87.

When you close the start button, 85 goes to +10.5 energizes the relay coil and pulls 87 to +12V. Since there is nothing to actively pull down 85(+12V stays on 85), when you open the ignition switch , 85 stays high because it is being pulled up by 87 and 87 stays high because 85 high(i.e. latch up at +12V). You have to disconnect the battery to have the relay go back to the open state.


The solution to this is to isolate the current flow between 85 and 87 by allowing current to only from from 85 to 87 and not back. The diode performs this function but with a forward drop so now you are at 9.7V instead on 10.5V.

Pos

Yes, a diode would work as you suggested, but let's take this a step further. By adding a diode you only provide a redundant path in case the relay fails. Theoretically, the relay could fail, you wouldn't know it, and you'd run until the diode fails, leaving you in the same position if you didn't carry a spare relay, or a jumper.

I guess what I'm trying to say, is that nothing is fool proof. In this case, you're just masking a failed component. Redundant paths are nice in aircraft where circuitry is used to detect failures, so they are addressed before the next flight, but in this case we have none.

It would be possible to put something in place, but is it worth it?

 

[MrZig]

Okay now I understand. The positive from the relay is simply making a long loop back through the relay's trigger keeping it open indefinitely. So there is no way a relay's output can hit a seperate positive source from the same battery or it'll always be a closed circuit. Makes complete sense.

Edit: Diagrams help me understand. Durr.

 

[p_s]

I guess what I'm trying to say, is that nothing is fool proof. In this case, you're just masking a failed component. Redundant paths are nice in aircraft where circuitry is used to detect failures, so they are addressed before the next flight, but in this case we have none.

It would be possible to put something in place, but is it worth it?

They make a click when they work & the 3 that have died on me stopped making a click when they died. On all 3, vibration caused one of the leads on the control side to come off & then short circuited, blowing a fuse. (And then a redundant circuit won't help.)

 

[reddirtrider]

They make a click when they work & the 3 that have died on me stopped making a click when they died. On all 3, vibration caused one of the leads on the control side to come off & then short circuited, blowing a fuse. (And then a redundant circuit won't help.)

I guess that's my point. Redundant circuits are not worth implimenting unless they are, first, truely redundant, and second, unless you know when the primary has failed and can fix it before the redundant fails.

Your leads are falling off due to vibration? No comment.

 

[posplayr]

Redrider

Redrider

I guess what I'm trying to say, is that nothing is fool proof. In this case, you're just masking a failed component. Redundant paths are nice in aircraft where circuitry is used to detect failures, so they are addressed before the next flight, but in this case we have none.

As you say you don't want to mask a failure and that is what you get with redundancy unless you can do Built In Test (BIT) to detect the failures.

I think a better solution might be to do a FET relay design and improve the intrinsic reliability. Otherwise just let it fail so you can swap another out.

P_S with three failures you should rethink your relay mounting strategy

Pos

 

[MrZig]

Has anyone had their relays fail closed?

I put a 30 amp relay in my Jeep to run an electric fan and every few months it'll stick closed and keep the fan turning when the trigger power source is disconnected. If I tap the relay it fixes this.

I suppose it could just be a faulty relay and the vast majority don't have this problem. Would suck to have it happen on a bike and have it kill your battery or worse.

 

[p_s]

P_S with three failures you should rethink your relay mounting strategy

They were all hanging loose on zipties. The first two were expensive (relatively) German relays that died after 3 blocks. The 3rd was a cheap Chinese relay & lasted 3k miles and then died on a freeway onramp in Seattle in morning rush hour. If it had failed 2 minutes later, I would have caused major congestion on a major bridge. I bought a new ignition switch after that, which solved the voltage drop problem.

Since November I've been using a relay for my heated grips that I rubber mounted. I'll see if it lasts longer.

 

[reddirtrider]

Has anyone had their relays fail closed?

I put a 30 amp relay in my Jeep to run an electric fan and every few months it'll stick closed and keep the fan turning when the trigger power source is disconnected. If I tap the relay it fixes this.

I suppose it could just be a faulty relay and the vast majority don't have this problem. Would suck to have it happen on a bike and have it kill your battery or worse.

Relays can fail closed due to arcing that welds the contacts together. Usually it's due to high inductance loads (your motor is one such load). These problems can be minimized by adding a free wheeling diode around the load. The diode can then supply the current the inductor needs when power is removed. Inductors cannot change current instantaniously and breaking their current with a relay will cause an arc.

 

[MrZig]

Relays can fail closed due to arcing that welds the contacts together. Usually it's due to high inductance loads (your motor is one such load). These problems can be minimized by adding a free wheeling diode around the load. The diode can then supply the current the inductor needs when power is removed. Inductors cannot change current instantaniously and breaking their current with a relay will cause an arc.

So you're saying that when power is shut off, the electromagnetic field that the motor generates sends off a voltage spike through it's wiring? Or perhaps maybe when I'm on the highway and the fan is turned off, yet rushing air is spinning the motor, and I turn it back on. Same concept. I'm probably wrong, but I'm not an electrical engineer. It interests me, though.

Now, because the coil is an inductive method, is there any possibility the coils could create such an effect? I don't think so, but then this is out of my league.

 

[reddirtrider]

So you're saying that when power is shut off, the electromagnetic field that the motor generates sends off a voltage spike through it's wiring? Or perhaps maybe when I'm on the highway and the fan is turned off, yet rushing air is spinning the motor, and I turn it back on. Same concept. I'm probably wrong, but I'm not an electrical engineer. It interests me, though.

Now, because the coil is an inductive method, is there any possibility the coils could create such an effect? I don't think so, but then this is out of my league.

I'm not sure of the inductances of the coils, so I can't say if they would cause this arc. If you want to be absolutely sure there is no arcing, place a diode from ground to the relay on the coil side. The anode should be ground and the cathode tied to the coil.

What happens when the relay is opened is that the voltage across the coil is reversed and the diode provides the coil the current it demands. The coil cannot immediately stop conducting current, so you need to let it die out on it's own. This is pretty standard stuff when dealing with inductive loads.

You can try the same thing on your motor load and see if it makes any difference.