f1rocket

f1rocket

Well Known Member
I need help for this electronically challenged brain of mine. I'm not even sure how to ask the question but I'll give it a try. Maybe some kind electrical engineer will take pity on me and provide an answer.

I am trying to drive a warning light when my 2-10 double-pole switch is in the middle position. In this situation, terminals 3 and 4 are open. Under all other conditions, terminals 2 and 5 are always grounded and terminals 1 and 6 are always powered. In the up position, 3 is open and in the down position, 4 is open. So the condition I am trying to pop the the light on for is when 3 and 4 are both open.

Okay, so I figure I need a relay to get this accomplished. I start looking at relays and some have 4 terminals and some have 8 terminals and I get totally confused. I found an 12 V/ 3A automative relay on Radio Shack seems like just what I need but the terminal designations have numbers on them and they don't make any sense. Here is a link to the spec sheet.

My question is 1) Is this the appropriate relay to accomplish what I am trying to do? 2) If not, which relay is? or 3) if so, how do I wire this relay up?

Thank you in advance. These electrons are very confusing!
 
Relay...

On the relay you show, when power is applied across terminals 30 and 87 (the ones that form a 'T'), the relay closes and contacts 86 and 87 are connected.

A diagram of the circuits involved would be most helpful. Getting the warning light ONLY in the middle position is a bit involved because the 2-10 is the progressive ON-ON-ON switch (typically used as a master switch).

To get the light to come on in either the middle or up postion (i.e. the master switch is ON):
In the MIDDLE position, contact 1 & 2 close (and stay closed in the UP position). If 1 is always powered, then in the middle position, 2 would also be powered. If you connected switch terminal 2 to terminal 30 of the relay, and grounded terminal 87 of the relay, it should close when your switch is in the middle or up position.
Your warning light should have one side connected to power and the othe side connected to terminal 86 of the relay. Terminal 87 of the relay should go to ground.

If you really want the light on in ONLY the middle position, you'll need a different realy - one that has a NC (normally closed) contact - easily obtained. But that circuit would need to be powered all the time to keep the light off. Knowing more about your circuits would be required.
 
Thanks Dennis. I have a 2-10 switch in front of the Master (also a 2-10 switch) to select which or both batteries are powering the starter. I have a PDF wiring diagram put together. I'll post it when I get home.

Yes, I need the light on just in the middle position but I'm not keen about powering the relay all the time. That would likely drain my battery between flights. Maybe I'll have to compromise and power it as you suggest, when the switch in on the "both" (middle) or "auxiliary" (up) battery position.

Thanks for helping me.
 
That's not correct!

DGlaeser said:
On the relay you show, when power is applied across terminals 30 and 87 (the ones that form a 'T'), the relay closes and contacts 86 and 87 are connected.
Click to expand...

Terminals 30 and 87 are the actual switch circuit(contacts) inside the relay. 30 is usually the power(or ground) source for the circuit you are switching. 87 goes to what ever you are turning off and on with the relay. The coil which pulls the relay down is on terminals 85 & 86. Some of these relays have a diode across these(85 & 86) terminals to prevent spikes, so polarity might matter. So if you apply power to 85 and ground to 86, the relay closes connecting 30 & 87.
 
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Oops!

Don Jones said:
Terminals 30 and 87 are the actual switch circuit(contacts) inside the relay. 30 is usually the power(or ground) source for the circuit you are switching. 87 goes to what ever you are turning off and on with the relay. The coil which pulls the relay down is on terminals 85 & 86. Some of these relays have a diode across these(85 & 86) terminals to prevent spikes, so polarity might matter. So if you apply power to 85 and ground to 86, the relay closes connecting 30 & 87.
Click to expand...
Don's right. must've had my tongue wrapped around my eyeteeth when I looked at the diagram...
 
Here's the link to my battery diagram. I'm trying to drive a light off the "Battery Source" switch when it is in the center, or "both" position. Thanks.
 
If your switch contacts are open in the centre position no problem Just put a lamp or an LED across them. When the switch is then closed the lamp will turn off. If using an LED put a 1k resistor in series with it and it will never blow out.
 
Norman,

I'm not sure I understand how this will work with a progressinve 2-10 switch. Can you elaborate? Also, I want the light to come on when the contacts are open, not go off. Thanks.
 
Rather than thinking about the switch behavior, look at the circuits being switched. If you're trying to determine that both battery contactors are closed (GND supplied to both coils), try this:
- connect terminal 85 to the switched power side of either battery contactor (those contactor outputs are connected together)
- connect terminal 86 to the switched side of the coil (GND supplied to turn on) for either of the battery contactors
- connect terminal 30 to the switched side of the coil for the other battery contactor
- connect terminal 87 to whatever load you have to turn on. GND will be supplied to it only when both battery contactors are turned on.

Bob
RV-10 N442PM (flying)
 
That's a tough one...

I don't see a 'simple' way to do what you want - just wires and a light.

The 'complex' way to do it is to add 2 relays in parallel with the solenoids - each one is activated with it's twin. Their contacts are hooked in series between the light and power source. When both relays are closed the light comes on. If either is off (it's solenoid twin is off) then the light is off.
You can get auto relays for a couple of bucks each, so the cost isn't high, it's just a bunch more wiring.

2 questions for my edification:
What drives the need for 2 batteries?
Does the Battery Link ACR manage the charging of the aux battery when the aux contactor is off?
 
Good idea!

bcondrey said:
Rather than thinking about the switch behavior, look at the circuits being switched. If you're trying to determine that both battery contactors are closed (GND supplied to both coils), try this:
- connect terminal 85 to the switched power side of either battery contactor (those contactor outputs are connected together)
- connect terminal 86 to the switched side of the coil (GND supplied to turn on) for either of the battery contactors
- connect terminal 30 to the switched side of the coil for the other battery contactor
- connect terminal 87 to whatever load you have to turn on. GND will be supplied to it only when both battery contactors are turned on.

Bob
RV-10 N442PM (flying)
Click to expand...
That's a cute way to do it with one relay instead of 2. The relay is in parallel with one of the solenoids, and it's switch is in series with the 2-10 contact that closes the other solenoid.
Good thinking out of the box!
 
Thanks Dennis.

I ended up with two batteries in a round about way. I bought the project off someone who wanted a dual battery system for redundancy and back-up purposes. I went simple VFR but I already had the batteries installed prior to purchase. On my previous Rocket, it was possible to draw down the primary battery during a hot engine start on an IO-540 that is fuel injected so I don't mind having the second battery. I've been considering ripping it out and simplifying though. I "really" don't need it.

Yes, the batteryLink ACR controls charging both batteries regardless of which one is "driving" the power to the bus. It also senses the differential voltages between the two batteries and it will isolate the bad battery from the circuit. Both the trickle charge voltage triggers and well as the lockout voltage differential are configurable. Blue Sea makes it and you can find the technical literature on their website.
 
bcondrey said:
Rather than thinking about the switch behavior, look at the circuits being switched. If you're trying to determine that both battery contactors are closed (GND supplied to both coils), try this:
- connect terminal 85 to the switched power side of either battery contactor (those contactor outputs are connected together)
- connect terminal 86 to the switched side of the coil (GND supplied to turn on) for either of the battery contactors
- connect terminal 30 to the switched side of the coil for the other battery contactor
- connect terminal 87 to whatever load you have to turn on. GND will be supplied to it only when both battery contactors are turned on.

Bob
RV-10 N442PM (flying)
Click to expand...

I think that's it!! (I think). I'll have to set down with a piece of paper and my pencil to verify but it looks good at first blush. Thank you very much Bob.
 
Nice!

bcondrey said:
Rather than thinking about the switch behavior, look at the circuits being switched. If you're trying to determine that both battery contactors are closed (GND supplied to both coils), try this:
- connect terminal 85 to the switched power side of either battery contactor (those contactor outputs are connected together)
- connect terminal 86 to the switched side of the coil (GND supplied to turn on) for either of the battery contactors
- connect terminal 30 to the switched side of the coil for the other battery contactor
- connect terminal 87 to whatever load you have to turn on. GND will be supplied to it only when both battery contactors are turned on.

Bob
RV-10 N442PM (flying)
Click to expand...

Simple, easy, 1 relay. I was going to accomplish this with a normally closed relay(5 terminal) but didn't like the relay being energized all the time that only 1 battery contactor was activated.
 
You're welcome! BTW thanks to Dennis for providing a decoder ring for those that didn't want to look at both the schematic and relay pinout to figure out what I was talking about.

Bob
RV-10 N442PM
 
Not so fast

Okay, I put pencil to paper and came up with something different. I don't think what was proposed will work, but I did find a solution that I think will work.

I am okay with connecting terminal 30 to the switched side of the coil on the primary battery contactor. Terminal 87 is then connected to my LED (with a stepping resistor) and then to ground. That provides the light circuit once the coil in the relay is energized. Okay, I'm cool to this point.

Instead of what was suggested for the two coil (85 and 86) terminals, it looks to me like I need to connect up 85 to the switched side of the coil of the auxiliary battery contactor. This will provide power to the coil. Then, 86 needs to go to ground. What was suggested seems to provide power up to both sides of the coil with no ground path.

Based upon the way the 2-10 switch works, when the switch is either up or down, then either the coil will not be powered OR the LED circuit will not be powered. When the switch is in the middle, both the coil and the light circuit are powered to ground. I think that gets it.

Does this make sense?
 
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Not sure I follow - reread Dennis' description. coil of a relay is in parallel with one of the battery contactors. The relay will then turn on/off with the same switching logic as that battery contactor. One of the relay contacts is then connected to the other battery contactor coil where the switch is connected. This means the other relay contact is grounded only when both battery contactors are turned on.

Above is a single relay circuit to drive an annunciator (active low) when both batteries are online. Maybe I'm missing something about logic that you're trying to implement, if so, sorry about the confusion...

Bob
RV-10 N442PM
 
I'm sorry, I'm as confused as ever. I updated the wiring diagram with one proposal, but I don't think this will work because the light will be on when the switch is in the middle or the up position. Please look at the wiring diagram and see if you can figure out which wire goes to which terminal. Thanks.
 
Ok, here you go!

f1rocket said:
I'm sorry, I'm as confused as ever. I updated the wiring diagram with one proposal, but I don't think this will work because the light will be on when the switch is in the middle or the up position. Please look at the wiring diagram and see if you can figure out which wire goes to which terminal. Thanks.
Click to expand...

First take the wire you have on terminal 86 of the relay and connect it to either Battery output from the contactors.

Next flip the led around and instead of connecting one side to ground, connect it to a switched power source(Buss)

You see, the relay is supplying ground for the led, not power.

When the switch is up as in the diagram, terminal 30 is receiving ground from the switch, but terminal 85 is actually getting a voltage from the ungrounded coil circuit in the contactor. Therfore the light will be off because the relay is not energized. This situation reverses with the switch in the down position. When both contactors are energized. Terminal 85 is grounded, terminal 30 is grounded, terminal 86 is receiving power from the output of the contactor, and the light is on!
Should work! Link to modified diagram below.

http://weflyforfun.com/battery.pdf
 
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Randy, below is what I'm thinking:

- relay terminals 85 & 86 (coil connection) across the coil on contactor A3
- relay terminal 30 to contactor A4 switched side of coil (which is also connected to switch A7 terminal 1)
- relay terminal 87 to the LED. This supplies ground or nothing, the other side of the LED will go to its power source.

If contactor A3 is on but A4 is off you'll have the relay on but no ground for the LED so it will remain off.
If contactor A4 is on but A3 is off the relay is off so the LED is off.
If contactor A3 is on AND A4 is on, the relay is on AND connects the LED to ground completing its power circuit.

Feel free to PM me if you want to discuss.

Bob
RV-10 N442PM
 
Don's diagram is the ticket...

Don's diagram shows the design that Bob described.
The key is that the LED must be connected to power on one side and use the relay for ground - which only happens when both battery contactors are activated.
The LED power can come from an always hot battery bus if desired, because it can only be activated if the master is on and the battery select switch is in the middle position.

Randy, at this point you're stuck with the dual battery design. All of us are going to be looking for that light when we run into you at OSH someday :rolleyes:
 
My contribution was intended to be notional to illustrate how to accomplish this but kind of turned into a lot more specifics than I'd intended without a little more thought.

If this is going to be implemented the power to the relay coil should come from a protected power source and not directly from the contactor which can source hundreds of amps. In fact, a small inline fuse supplying power to both the relay coil and LED would be a really simply way to approach this. Worst case is the fuse blows and the light doesn't work. Since you go through the middle position to get to the "normal" position, a quick check to see that the light comes on will tell you that all is well with the fuse.

Bob
RV-10 N442PM
 
A Big Thank You

Thank you all for your help on this. I can't say enough about your willingness to share your expertise. I was pulling my hair out.

I've updated my drawing to provide protection to the circuit.

I should be at AirVenture next year, and that warning light will be there. Look for the Maroon and Gold Rocket with the Tan leather interior. First beer is on me.

Here's the link to the Final Drawing.
 
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Happy to help and glad it all came together! I'll keep an eye out for the F1 at OSH this year. Stop by and we'll trade beers - I'm usually in the RV-10 camping area in Camp Scholler in the evenings along with a lot of other beer aficionados...

Bob
RV-10 N442PM
 
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