Relay stutter

[Madcow]

It may be that I've finally solved the mystery!

Recap: For those of us who have tried to wire a MR sound board with a relay (to allow full current to a K2 LED), it seems that any MR board other than the Mace, produces an annoying stutter effect that prevents the saber from turning on.

I recently wired up a mace board, Royal Blue K2, and a 4.8v rechargeable cell... and it stuttered!!!
So I continued experimenting and finally found that when I run 2 seperate power wires (one to the red and orange wires on the board, and one to the LED/relay) it helped. Then I made the power wire to the LED/relay much longer (looped it back and forth) it solved the problem entirely! I don't know why it works but it does!
http://rpetkau.photosite.com/Album7/IMG_1139.html

I have not tried it with my Luke board yet.

Post your results!

MC

[/img]

[Strydur]

By making the wire longer you are adding resistance. Try putting a really low rated resistor in line and see what that does.

[xwingband]

I tried a diode (at Do-Clo's suggestion) with my Ani board so I'm not sure resistance is what up is up with it there.

I think I'm lost on the two power leads thing there. Perhaps a diagram would help there?

[Firebird21]

If the resistor doesn't do the trick then it may be a case of a magnetic field being created by you looping the wire. It may also have something to do with the radio emotions the resistor puts off.

I don't fully understand this phenomenon, but I do know that I have a wireless mouse that when I coiled the wire from the receiver to the PC it didn't work, when I uncoiled it, it worked fine.


Just a thought...

[Madcow]

I thought it was resistance too, but I tried both a 1 ohm and a 3.3 ohm resistor on the LED and it didn't seem to affect it at all. Somehow the pos. wire to the LED being 10 inches longer than the one to the sound board makes a difference. I'm using 26 guage stranded wire - 10 inches shouldnt affect the resistance that much... right?

Looks like this:
http://rpetkau.photosite.com/~photos...1952348874.jpg

MC

[erv]

It could be a side effect of the fact that you are using a relay.
To diagnose this, please allow me to ask a few questions :
- does the problem occurs when the Luxeon is not there ? (the relay just clicks once ?)
- is your really a model with roll-off diode ? An inductive load is quite bad on a transistor commutation schematic like the MR board, you need a roll-off diode in // with the coil of the relay.
Erv'

[xwingband]

The same one I used on your old set of boards was what I used when I tried it (I'd have to look up the number/name). I thought it wasn't a bad idea since when the batteries were low it didn't do it as much if at all.

[erv]

if you want to check if your relay has a roll-off diode or not, simply use a ohmmeter and diode checker.
In ohm-meter, the coil is seen as a resistor for both polarities, about 100's of ohm. Go into diode check mode : you should read around .700 v in one polarity, and infinite on the other polarity (and this last point means that you have a diode).
If the relay doesn't have one embedded, wire an 1N4001 this way


and test to see if you still have the problem.

Erv'

[Madcow]

Thanks Erv,
I'm pretty sure the relay doesn't have a diode.

To answer your questions...
When the LED is not on the circut the relay works fine - in fact - this mace board works fine with a 3 watt lux on the relay. the Luke board I had the same problem with worked fine with a 1 watt lux. It only stutters when the heavy drain of the K2 is added. This led me to imagine that...
The instant the relay switches and the K2 draws power - the power drain disrupts the MR boards startup sequence... shutting off/trying to start again etc. in a cycle.
(What do you think of this theory Erv?)

I don't understand the need for a transistor in your schematic.

X-wing, did a diode parallel to the relay coil work in your application with a K2 and MR board?

MC

[erv]

Hi MadCow,
you don't need a transistor here, the transistor is already there on the MR board (6 transistors in common ground actually). You're probably right MC, you get a little shortage of voltage when the power comes to the K2. It's so sudden that it causes the board to reset or go off (this is called a brown out reset on certain microcontroller chips). And then you get this oscillation phenomeon. Using a diode would not help it so much, but it should be tested. The role of the roll-off diode is when you cut the power on the relay : the self inductance of the relay coil stores current. When you turn off the relay, there is a big gap ofvoltage that generate some current... that goes backward in the circuit thru the positive wire. The roll-off diode absorbs this current at that moment and protects the circuit. But if there was a problem about this, it would occurs even without the luxeon plugged. However, it can be a combination of both phenomenoms.
Now, why is it working with some wire lenghts ? Just because you created another self inductance (a coil) by attaching the wire with many turns. A coil smoothen the current during the power on of the luxeon, and avoids the reset of the board. The main problem here is that the relay turn on and off the luxeon in a very sudden way, while the proper way would be to have soft start. The other problem is that you're taking the power of the lux directly on the batteries, not on the board. The solution would be to regulate the voltage of the board, with a little voltage regulator to make sure it does not reboot, cause an inductive load on the relay is not the best thing (well, okay, I'm proposing damn complicated things while your solution works )

would someone like a schematic to sum it up ?

Erv'