trenace
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posted August 26, 2005 06:59 PM
Electrical question: Relay that holds circuit open (off) not closed?
Does anyone know if there is such a thing as relays that, when current is applied, OPENS a circuit instead of closing it, and has no problem holding the circuit open indefinitely and reliably?
And if so, where to get it?
It occurs to me that if I had such a relay, then I could use it to have the headlight voltage serve to open (switch off) the connection to a battery that I don't want connected while the engine is running. Every time the bike is turned off, the circuit would re-close, so that it would be closed (battery connected and providing juice) when the ignition is turned on, up to the point where the engine "catches" and the headlights come on.
Thanks!
  
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ZXLNT
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posted August 26, 2005 10:07 PM
Yep a silicon controlled rectifier will probably do that, and then use it to trigger a normally closed relay, that will open when the SCR trips it..
http://www.play-hookey.com/semiconductors/scr.html
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trenace
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posted August 26, 2005 10:30 PM
 Edited By: trenace on 26 Aug 2005 23:43
Thank you!!!
Looks like I could get two 5-amp ones from DigiKey, as I imagine the bike might draw 10 amps of current with the ignition on but motor not running, headlights off, and no parking light and LED for taillights. Could be the solution!
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ZXLNT
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posted August 26, 2005 10:41 PM
Use the SCR to switch the relay. You can use a resistor on the gate to limit current, then use the relay to switch hi-power..
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trenace
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posted August 26, 2005 10:44 PM
Edited By: trenace on 26 Aug 2005 23:46
Um, wait a sec... the "normally closed relay".... do I need the SCR?
If there's a "normally closed relay" then won't triggering that open it?
And so couldn't the headlight voltage itself trigger that relay without needing the SCR?
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ZXLNT
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posted August 26, 2005 10:45 PM
Okie doke..
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trenace
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posted August 26, 2005 10:46 PM
(I edited again... could you check again? Thanks!)
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ZXLNT
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posted August 26, 2005 10:47 PM
Exactly what are you wanting/trying to do..
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trenace
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posted August 26, 2005 10:51 PM
Edited By: trenace on 26 Aug 2005 23:54
I have a LiPoly battery that will have two functions:
1) Connected to starter motor relay. This connection, to the input of that relay, can be connected at all times.
2) Connecting to the positive "mains" of the bike ONLY when motor is not running. When motor is running, this should NOT be connected, as I don't want it discharging into the main electrical system nor do I want the battery being charged by the bike.
So my idea is, a relay that connects the LiPoly to the bike's "positive mains" until the headlights get power, at which point the relay opens. (The 12 does not send power to the headlights when the key is first turned on, not doing so till the starter disengages.)
So there is such a thing as a "normally open relay" and that's the term for it, I've learned from you.
So a "single pole single throw normally open relay, " e.g. any of these, will do this?
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ZXLNT
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posted August 26, 2005 10:56 PM
You have normally open relays and normally closed relays. Just like it sounds. One closes the contact when triggered, the other opens the contact when triggered. You could pick the voltage off the stator winding that goes to the headlight relay. When the voltage rises enough to trip the relay it will open the contact cutting the electrical circuit to the "mains" as you describe it. Only thing I dont know is what voltage the winding from the stator has to trip the relay and at what point that output reaches maximum, shouldn't be too hard to check with a multimeter.
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trenace
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posted August 26, 2005 11:01 PM
Edited By: trenace on 27 Aug 2005 00:04
Looks at DigiKey you get your choice... I picked 12 volts for the coil voltage.
Actually the idea was to use the voltage after the headlight relay as the signal to trigger the normally closed relay to disconnect the battery from the "mains."
I just didn't know that there was such a thing or the terminlogy for it... by telling me that phrase, I think that I found it in the DigiKey, if it seems to you that such a part wired that way would do that job?
I guess I have a choice between part 1 and part 2, the difference being the first is described as having "QC Terminal" mounting and the second "Screw." Don't know exactly what they're talking about but I guess either would be workable, if the correct part type in the first place?
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ZXLNT
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posted August 26, 2005 11:05 PM
Hang on its gonna be a bit. Just got a shooting. I work in 911 center..
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trenace
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posted August 26, 2005 11:27 PM
Edited By: trenace on 27 Aug 2005 00:36
Hope that goes well!
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ZXLNT
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posted August 26, 2005 11:44 PM
Christ and now a car chase and a rollover accident and now a house fire....
All hell just broke loose..
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trenace
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posted August 26, 2005 11:50 PM
Edited By: trenace on 27 Aug 2005 00:52
Oh man, you definitely have your hands full, don't worry about this.
Actually it seems to me I had it backwards, I need a "normally closed" relay. That is, if "normally" means when there is NO signal voltage. Is that the meaning?
It would open (disconnect the LiPoly from the bike's "mains") on getting the positive voltage from the headlight signal. Do I finally have it right? (Again, this can wait, you do have your hands full!)
Thanks!
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ZXLNT
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posted August 27, 2005 12:03 AM
Yes correct
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trenace
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posted August 27, 2005 12:11 AM
Thanks! I'll order one and give it a try!
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pdb1964
Zone Head
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posted August 27, 2005 09:50 AM
How would a soleniod work for you? Current keeps it open. No current, spring closes the circuit.
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trenace
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posted August 27, 2005 11:51 AM
Edited By: trenace on 27 Aug 2005 13:23
THat could do it too, makes sense. Though as you say it would depend on current rather than voltage, so I'd need the full headlight current probably running to it instead of just a light-gauge wire tapping the voltage.
Too late now in any case, turned out Radio Shack -- ugh -- had a relay that seemed suitable so just bought it now, guess I will know shortly if it works! (BTW, if it does, I will surely order another one from DigiKey and swap it out.)
Thanks!
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soldier7
Parking Attendant
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posted April 25, 2012 07:32 PM
Hi, I have a couple of elec question for my 2005 zx12 if someone can help me.
(1) I know that the Speed Sensor supply voltage gets its power from the clock meter, but does anyone know what the "Volts and Amps" are that are coming from the clock to the Sensor????
(2) I dont have the stock gauge meter on my bike so there is no where to connect the "#11 wire - fuel reserve switch" to. What does this wire do, can I just leave it or do I need to connect it to a manual toggle switch in order to turn on my fuel reserve???
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