Printer Friendly Forum Posts - does this relay exist?

I guess the moderator changed my title.

No problem

But I must also add that I want to know if it is possible even if the relay does not exist?

Pretty much anything's possible, but I'm not sure what that relay's supposed to do.
What current is changing from power on to power off? Are you trying to detect a change in current or voltage?

Sure, there are current-sensing relays but I second the above question: what is it you are trying to accomplish?

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The constant power would be power from the battery of a car. Always on.
The alternating power would be the inition power from the car.
The 12 Volt pulse would be to activate an accessory.

What I would want is for the accessory to activate each time the car is turn off ot turned on or each time the power state changed.

Alternating is usually used when referring to alternating current, or AC (as opposed to direct current, DC), that was what seemed confusing. I think you're referring to the toggling of the ignition switch on or off.

From what I can make out of the description, I guess you just want a pulse output when your ignition is either turned on or off. Easy enough, but not sure what you mean by "each time the power state changed".
Power state of what?

You have it dead on. I used the term CHANGE OF STATE because I have found it in some of my research online. I assume I am using it incorrectly.

I am a NOVICE and I KNOW IT.

LOL

This is a way you can do it using a 20 cent part-

Thank you very much. I have to translate the symbols and markings, but this is a great start. Thanks

dualsport wrote:

This is a way you can do it using a 20 cent part-

Thanks for the diagram. Now I need some help identifying whatis what. Below I have listed what I do not know, which is mostly everything.

Mouser Part #: 511-4070
Manufacturer Part #: HCF4070BEY
Description: 5V Logic (HCF4xxx, M74HC/HCT, 74AC/ACT, 74VHC/VHCT) Quad Exclusive OR

R1: 100K Resister

C1 4.7uF: ?????

Q1 BS170: ????

D1N4001: ????

Relay COM: ????

Relay NO: ????

Any help would be greatly appreciated.

The only parts that you might need to handle differently are the Q1 transistor (BS-170) and the XOR logic gate HCF4070BEY.
You can find them both on www.mouser.com (just type in the part on their search bar), and they have datasheets that you can look at there. The numbers on each of the pins correspond to pins on the chip, and you would just need to connect wires between them to the corresponding parts.

The resistor, cap, diode and relay are run of the mill kind of parts that don't need any special handling. Tolerances on them are not at all critical, since you'll probably want to experiment with different values to get different pulse time, so you can just get the cheapest one they have. Don't get the tiny surface mount type of parts because you'd probably have a hard time connecting them up.

Ok, this is what I found. I have specs on specific ones but I want to make sure I have the right items.

Mouser Part #: 511-4070
Manufacturer Part #: HCF4070BEY
Description: 5V Logic (HCF4xxx, M74HC/HCT, 74AC/ACT, 74VHC/VHCT) Quad Exclusive OR

R1: 100K Resister

C1 4.7uF: C Series Capacitor

Q1 BS170: Tilt Switches

D1N4001: General Purpose Rectifiers

Relay COM: Non-latching Single Relay

Relay NO: Solid State Relay

The relay is just a single relay, not two separate items.
The relay NO stands for Normally Open contact terminal of the relay, and Relay COM stands for the Common terminal. All on the same relay. A standard automotive SPDT (Single Pole Double Throw) relay would work. You can get that from alarm supply places.
What exactly are you using this for? Maybe you don't even need a relay, if you don't need a lot of current drive.

The BS170 is the one several lines down, not the tilt switch one:
BS170 link

The other stuff should be okay.

IT is going to deliver a 12 Volt pulse to operate my power folding mirrors when the car is turned on and turned off. What lead is the pulse delivered through? Is it the 30 Lead on the SPDT relay?

Basically the relay is acting as a switch, whatever you connect to the COM and NO terminals get shorted together when it actuates.
If you connect COM to your mirror, and 12V power to the NO contact, then the 12V passes through to the COM terminal from your 12V power input.

Does your power mirror really work from a single short pulse, or does it need to be powered for the time that it takes to move the mirror into position? If the mirror isn't designed with a latching circuit already, I would think it takes more than 1/2 sec to move.
I'd also consider what might happen if it gets out of sync; it might then fold your mirrors up when you turn the car on, instead of what you probably want.

This is not connecting directly to the folcing wires of the mirrors. It is going to splice in the controller button to simulat a buttong push. IT only takes a short pulse fromt the button to activate the mirrors. The there is relay built by honda that powers the mirros after the button is pushed.

I am still a little confused. There are a total of 5 connections.

1 connects to the ignition

2 connect to grounds.

the other 2 are what you just went over above. The problem I am having is I did not have an additional 12V power source set aside for the SPDT relay. I thought the inigition would deliver the power.

Do you have a yahoo or msn messenger ID so we can discuss this live?

The mirrors work similar to windows I have been told. Folding and unfolding based on the direction of current threw 2 wires. Are the 2 connections coming out of the relay, 87 & 87A working the same way? reverseing current based on the operation needed? IF so, that would not be what is needed. Just need a simple 12 volt pulse to simulate the control buttong being pused and then letting the system do the rest.

The preluse is one of the only hondas that you do not have to hold the button down to get the mirrors to fold all the way in so that is why I speculate a single 12 volt pulse spliced into the control wire would be the easiest way to get this done.

I'd measure the wire that you're planning to tap into and send the 12V pulse to make sure that it just goes to 12V temporarily when you push the button. If it does, and doesn't show a ground when it's not being pushed, it sounds like you should be able to do this.

Also, the Relay Common can be connect to the chasis or must it be connected to a common line?

Relay Open is delivering the pulse and is spliced into the line assuming all I need is a singal pulse?

Are these correct?

If you need a 12V pulse, the relay common would be connected to a 12V source. The relay Normally Open would be delivering the pulse out to your line; it's basically like a switch connecting the common to the normally open.
Is there anyone you know that has some experience with relays that can help you do this? Just wouldn't want you to accidentally blow something, since it sounds like you haven't done any of this before.
Really should fully check your input line to the mirrors to make sure you can just connect 12V to it without damaging anything.
I'd use an inline resistor or a brake light bulb to limit the current if things aren't as you expected, at least when you test it for the first time..

I am not going to start anyhting until I fully understand the situation both in your circuit and in the car. I ask alot of questions because I have not done this, but I am not afraid of what I do not know.

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This is the part I am a fuzzy about. The other end of the diagram is connected to the inigition. Am I wrong for thinking this is a power source, similar to the inition power source on a radio?

The "ign switch" input shown is just what you originally mentioned as the "alternating power" source; it would just go to 12V when you turn the ignition on, and go turn off to 0V when you shut down the car.

It's not being used for power, but just as the control for the circuit so it knows when to put out the momentary pulse.
If it's prone to glitches or your mirror trigger input is sensitive to short spikes you can clean up the signal with a Schmitt trigger, but we'll deal with it later only if necessary.

Ok, I understand now.

IGN = The ignition power source

Relay NO = Delivering Pulse

Relay COM = Constant 12V power source