dei528t relay w/ hid kit

OK! I figured it out, finally! I'll post my diagram and hopefully help others from days of frustration. - Shawn

You might want to check the voltage on the relay after it turns on. Depending on the relay you're using, it's going to drop across your resistor. Not having full drive voltage on the relay reduces the force on the relay contacts, which may cause problems if you're pulling a lot of current through them.

viperspike wrote: I was using 2 9V batteries in series to test my circut off the bike, however upon using 12V it did not work properly. First, I believe that the capacitor has to charge to about 7 volts **before the timer (MK111) will start the delay cycle. I am now using a 450Pf capacitor with a 10ohm resistor.

Is that pF as in pico Farad? That's a very small value that would have almost no effect here. But if it's a PF as in peta Farad, that's immense- Is that what's marked on it? Anyway, it's the resistor that determines the amount of current that the relay gets, so that's why you found that you had to drop the value down from 150 to 10.   That should allow enough voltage to power the relay, with the size of the cap affecting the delay.

upon testing the original 150ohm/4700pF cap the MK111 led would stay on forever and never close the circuit. (stayed in the delay position) I then added another 150ohm resistor in parallel dropping the resistance to ~70 and the MK111 still would not close. So I added a third resistor dropping to ~30ohms = same result Tried a 2200pf Capacitor w 30ohms = same result (stuck in open position forever) Tried a 470pf capacitor with 10ohm and found it stayed open forever with the bike off, but with engine running the alternator charges the system to ~14 or so the MK111 delays for about 30sec (its slightly adjustable, not like without the cap/resistor combo) and upon closing, the ground relay is delayed ~1/2 second. !! the 470pf cap I used is a 50V capacitor, that could be my problem, but it seems to work okay - Shawn

Instead of a capacitor and resistor would a 5.1V zener diode to prevent unwanted momentary actuation of the second (grounding) relay? Any thoughts? - Thanks - Shawn

Not sure what you'd do with a zener. How are you planning to use one here? If you really want to do a fixed time delay you should use transistor drivers with resistor/cap to set the timing. Problem you'd have with the setup you're using is the reduced relay coil drive voltage. If it's too low, it reduces the contact force on the relay, and increases resistance. Get to a certain point, and the contact will heat up and eventually fail because it'll degrade and pull more current because of the lower voltage. HID ballasts are a constant power device, so if you feed it lower voltage, it'll start drawing more and more current to compensate. If your relay contact starts down the slope, it'll get worse and worse as it's called on to pass more current even as it's less able to do so. I suspect your circuit isn't actually using the capacitor at all, but just the reduced voltage causing the weak relay pull in. When you start the bike, the vibrations may be shaking the relay and allowing it to close the contacts. My recommendation would be just to simply install a switch to control it manually or use the relay circuit posted earlier to use the starting of the bike to switch in the HID power.

Thanks Dual - you saved me saying it. Not that I ever like time delays involving the relay coil (it should be buffered via a transistor or FET, from an RC or timer circuit), but a resistor in series with a relay (coil) is also trouble - unless you have a BIG cap (usually electrolytic which is expensive, and has limited life).

oldspark wrote: BIG cap

Yeah, I know it's popular to use the BIG cap here for delays mainly because it seems simpler and more intuitive, but it's probably just because MOSFETs are not that familiar a device to some.

Plus it's in the list of suggested relay configurations here, so it's sorta got the seal of approval. 

Using a 20 cent transistor along with some penny parts for the relay driver in those applications is so much better than a big moosey cap it just seems odd why it's not SOP. 

Thanks again Dual. Not that I mention MOSFETs for simple RC delays - I'm not that good on circuitry either, and FETs are hi-impedance voltage switched devices (unlike lower current-switched transistors) - but they seem excellent for hi-current on-off applications. IE - I often see 60A devices for a few dollars (AUD$2). And being hi-impedance inputs, current-drive is not a problem. (That should make it simpler for RC control as the FET itself is usually insignificant as an RC drain.) Alas it's one of those "break even" decisions.... When is a timing buffer and its complication (transistor(s) etc, else a 555 or other circuits) better than relay chirp and unreliability, big caps & cost, difficult adjustment, etc?