5 pin relay wiring Question

[5-90]

I have a relay question and i figured i would post it in this thread...

I have both SPST and SPDT relays that im wiring up. Im using the SPDT Relays as SPST's (basically just not using 87a).

From what i understand, 85 and 86 on the relay can be wired anyway you want too. So the switched +12v can go to either 85 or 86 as long as the other is used for ground.

Is the same principle true for 30 and 87? When the coil is energized and the internal switch closes completing the connection between 30 and 87 i wouldnt think it would matter which way the voltage and current is flowing... Am i wrong here?

I started wiring everything up and realized i was wiring them to have 87 the fused constant +12v... so i dont want to re-wire..lol

Advice is appreciated. Thanks!

85 and 86 are not polarised, and can be wired either way. Convention is for 85 to go to the signal, and 86 to earth.

30 and 87 are likewise not polarised, and can also be wired either way (for use as an SPST relay.) It is convention for pin 30 to be the power source (with any variant,) and 87/87a to be the outputs.

Yes, you can make pin 87 your power source from a practical view - but I don't suggest it. Anyone working on it later will think that pin 30 is "always hot" and pin 87 will be "switched hot" - and when it's been reversed, accidents have a greater probability of happening.

 

[Southwest Chuck]

Correct.

If it's a 4-pin relay, it's an SPST. The fourth pin (usually pin 87 on DIN relays) is either ON or OFF. Terminals are usually numbered 30-85-86-87.

If it's a five-pin relay, it will be either SPDT or DPST - and you can tell either by the terminal numbering or the diagram that is usually either printed on or moulded into the case.

If the pins are numbered 30-85-86-87-87a, it's an SPDT relay. Pin 87 is OFF and pin 87a is ON, until the relay is tripped (then pin 87 is ON and 87a is OFF.) This type is also called a "changeover" relay, and is probably the most common DIN relay going.

If the pins are numbered 30-85-86-87-87, it's a DPST relay. Pin 87 (both of them) will behave as pin 87 in both other types of relay - you just have two of them.

Wiring conventions:
Pin 30 is the power source - this is the one that gets wired directly from the battery, the alternator, distribution, or whatever. This lead had damn well better be fused going in!
Pin 85 is the "signal" to the relay. This is the one that will come from the low-current switch you're using, be it a toggle, press button, vacuum-actuated, thermal switch, or whatever.
Pin 86 is the ground for the coil - this is the one that goes to a convenient earth terminal somewhere.
Pin 87 & 87a are for the loads. You'll usually use pin 87 for common loads - the idea behind having pin 87 and pin 87a is to provide a "logical OR" for switching back and forth between loads. Pin 87a usually goes unused.

All three relay types may be used as an SPST relay, and you can replace the four-pin relay with either of the five-pin relays, if that's all you have to hand and there are five cavities in the socket (usually the centre one isn't wired.) Check your wiring before you do the swap - and especially check if you want to switch off between the SPDT and DPST relays...

SPST - Single Pole Single Throw. Switches a single circuit either ON or OFF.
DPST - Double Pole Single Throw. Switches two circuits ON or OFF in tandem
SPDT - Single Pole Double Throw. Switches a single circuit between two possible states, as a "one or the other" option ("logical OR.")

The typical DIN relay uses about 100-150mA for the coil, so you can go down to 18AWG handily with wiring for that side. Terminal-side wiring should be sized and fused according to demand (and not necessarily to the relay capacity. You can use wiring suitable for 30A if you think you might use it for something else - then you just switch the fuse for the load you're using. However, the fuse should always be sized according to actual demand, and not circuit capacity (if you overbuild it.) If you have a power consumer rated for 10A, you can build the circuit for 30A, but the fuse had damn well better be a 10A job...

Question: is the hi/lo beam switch on the column basically a relay, turning the low-beams off and the hi-beams on (or vise-versa) when switched? (I think not, though, now that I think about it). The reason I was asking, was that when I pull the signal lever back to switch to hi-beams, and hold it in the retracted position, both lo and hi are on simultaneously. When released, low beams go off and Hi's stay on (and again, vise-versa). I guess that means it's just a switch, not a relay, right?

I think I'll do a search to see if they can be modified to allow both hi and low to operate at the same time on my '94......hmm....

 

[Matthew Currie]

Question: is the hi/lo beam switch on the column basically a relay, turning the low-beams off and the hi-beams on (or vise-versa) when switched? (I think not, though, now that I think about it). The reason I was asking, was that when I pull the signal lever back to switch to hi-beams, and hold it in the retracted position, both lo and hi are on simultaneously. When released, low beams go off and Hi's stay on (and again, vise-versa). I guess that means it's just a switch, not a relay, right?

I think I'll do a search to see if they can be modified to allow both hi and low to operate at the same time on my '94......hmm....

I don't think there's a relay in that system - the hi-lo switch is mechanically actuated by the lever. You could, however, have the high beam circuit actuate a relay that then actuates the lows, or simply bypass the dimmer switch so the lows are on whenever headlights are on.

However, it's not generally a good idea to run both beams at once, because, first of all, you'll burn out bulbs faster, and second, if your high beams are excessively bright, your eyes will adjust to them, and you'll see less well when you switch to low.

You can experiment with this a little, by holding the switch in "both beam" position for a while as you drive, and then hitting the dimmer switch. See how poor your vision suddenly seems.

 

[Southwest Chuck]

Naw, would'nt use them for hi-way use, just for off- road, call it a poor man's off-road light system! LOL :wave1::wave1:

 

[Matthew Currie]

Naw, would'nt use them for hi-way use, just for off- road, call it a poor man's off-road light system! LOL :wave1::wave1:

For that, then, I think your simplest solution is to tap into the wire that goes from headlight switch through dimmer switch to low beam, and bypass the dimmer switch. Put a toggle switch in the bypass, and you're good to go. Carry an extra sealed beam or two so that if you blow your lights on a bumpy trail, you can get home the same night.

 

[cialert]

I would say that 14awg that will handle 15 amps should be more than adequate for the typical aftermarket in dash headunit.

it clearly depends on what gauged wire you use. i know for a fact that if you have 15 amps though a 14 gauged wire, it can be rated safely up to 20 feet. if you add another ten or even five feet to that 14 gauged wire youll have to get a fatter wire to do the job otherwize your wire would overheat, melt, then your wire is exposed and more prone to a car fire, but thats worse case. and that wont happen at the start. hope this gives poeple an insight on different gauged wires rated to how many feet.

 

[kastein]

14 gauge is good for up to 15 amps for any distance (safe enough that the government/insurance companies will let you put it in the walls of your house, even.) 12 gauge is good for up to 20 amps. You can get away with more current over shorter distances in free air (i.e. "chassis wiring" in an appliance cabinet) but those numbers are good for any distance. Check the national electric code handbook for other gauges and specs, those numbers assume 60Hz AC but are a good baseline for DC as well, because only wire thicker than 4/0 gauge is actually affected by the skin effect.

See http://www.powerstream.com/Wire_Size.htm for more wire current ratings.

 

[RCP Phx]

14 gauge is good for up to 15 amps for any distance (safe enough that the government/insurance companies will let you put it in the walls of your house, even.) 12 gauge is good for up to 20 amps. You can get away with more current over shorter distances in free air (i.e. "chassis wiring" in an appliance cabinet) but those numbers are good for any distance. Check the national electric code handbook for other gauges and specs, those numbers assume 60Hz AC but are a good baseline for DC as well, because only wire thicker than 4/0 gauge is actually affected by the skin effect.

See http://www.powerstream.com/Wire_Size.htm for more wire current ratings.

It also depends on the type of wire.Automotive wire like welding wire can handle alot more current than standard building wire types.Even the specialty(building) wires like SIS will carry more current than THWN,its all about the stranding and insulation type(you cant even burn SIS).Aircraft wire is another exceptional product that will withstand extreme conditions.
And sorry I know this is an old thread!

 

[kastein]

Yeah, I love my Teflon-insulated silver-plated stranded wire... got a boatload of it for free a while ago It definitely is heavily influenced by how many strands the wire is (at higher AC frequencies) as you said, and by insulation material / ambient temperature / acceptable voltage drop as well.

http://www.logwell.com/tech/shdwe/teflon_wire.html - such great stuff the military uses it.

 

[yossarian19]

Does anyone have a part number for an ISO Mini 5-pin dual-87 (NOT changeover, dual output) relay? I'm trying to order them at work (I'm lazy / cheap) and can't find them in our parts vendor's program.

 

[ParadiseXJ]

Or I could quit dickin around and just wire it up using only one pin...

Thanks for the replys, hope this help in someones future search!

Just go with the one pin IMHO.

K.I.S.S. always works when in doubt.:farmer: