At 10:44 AM 9/3/04, you wrote:
> Yeah, this wasn't a "standard" relay like what most people would think
>of, it had a slightly different form factor, but it operated the same as
>a standard 4 terminal relay. Actually, there is a 5 terminal version
>of the standard 4 terminal relay, its got an extra terminal, usually right
>in the middle. A "standard" 4 terminal relay has the 2 terminals for the
>coil (12v switched source and ground) 85 and 86, then the 2 terminals for
>the switched circuit (12v source - 30) and the output to accessory (87).
>The 5 pin relay ads the 87a terminal, which is connected to the
>12v source (30) when the coil is *not* energized. (In the proper
>electrical terminology, its a "normally closed" switch as opposed to a
>"normally open" switch. 5 terminal relays with both 87 and 87a pins
>are both normally open and normally closed relays, they can be used for
>either one, or both at the same time (almost like 2 relays in one) :-)
> -Jon-
The 5-pin relay is commonly called a Bosch relay but is made by other
manufacturers (Siemens, Potter& Brumfield, etc.). They are the most
widely used, versatile and can handle up to 30 amps, which is more than
suitable for most applications.
The 30 pin is set perpendicular to the other pins. Normally, it doesn't
matter which way you pass the current on the 85 and 86 coil pins because
if you hook it up backwards, the coil will still activate the relay.
However, relays sometimes have an odd tendency to turn themselves back
on briefly. To counter this, a diode ( a 1-way switch) is placed between
85 and 86. This is referred to as a tamping diode. A diode wall has a very
high resistance in the opposite direction. When a tamping diode is used,
it is important that the coil is hooked up according to polarity. If a tamping
diode is used and it's hooked up backwards, the result is essentially like
shorting a wire out, which will likely burn something up eventually :-(
I'm just wondering if what you were experiencing was this odd tendency.
DMLers do seem to have odd tendencies :-P
Bob
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