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xxbaker  
#1 Posted : Sunday, July 25, 2010 10:13:04 PM(UTC)
xxbaker

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Background information: I have 15VDC feeding into the JT module. I also have some input and output relays that are switched on and off this supply as well.

When I first turn on my amp, my JT works perfectly. Turning the knob causes the volume to raise and lower, there is no distortion or anything and it all sounds and works great. No matter how many times I turn the volume or leave the amp on, the JT works perfectly. If I start switching inputs or outputs (turning on and off different relays on the same 15VDC circuit as the JT) the JT "turns off." It doesn't happen every time a relay is switched, but after about 3-4 turning on and off of different relays, the JT will usually be "turned off."

What I mean by turned off is that it stops responding to turning the volume knob. The relays currently on stay on - that is the volume stays at it's current level, but turning the volume knob down to mute has no effect on the attenuation.

Measuring voltage I have seen that it will fluctuate somewhat when turning on and off different relays, but the JT should be regulated and therefore it should be shielded from this effect no? And if not, why does it stay at a single volume and not mute as if it were receiving no power at all? I'm assuming the volumite is what is being disturbed and that's why it holds a volume, but that voltage seems to be rock solid when switching relays (as it's driven from the JT board).

If you have any ideas as to how I can/should fix this or why this is happening let me know.
Brian Donegan  
#2 Posted : Monday, July 26, 2010 3:58:55 AM(UTC)
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Can you post a diagram of how you have your relays wired? A photo might do it.
xxbaker  
#3 Posted : Tuesday, July 27, 2010 12:47:12 AM(UTC)
xxbaker

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Here's a picture of how it's wired up. There's more than 3 relays (about 9 total, but only 3 max are on at one time), but they're all wired in parallel with switches controlling which ones are on. The relay driver module is connected to this same power supply and then is hooked up regularly (the volumite and relay boards are all hooked up as they're supposed to be. I'm not sure how helpful this diagram is as I couldn't make a neat one that would show all the relays with my current means, but hopefully it'll clear up what I mean.

UserPostedImage
Brian Donegan  
#4 Posted : Tuesday, July 27, 2010 4:11:25 AM(UTC)
Brian Donegan

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How are you getting the 15vdc? If you are using a transformer, it would probably be better to power the JT from it directly.

The problem is clearly voltage spikes or dropouts causing the JT microcontroller to freeze up.

You should have diodes across the coils of each of your relays to prevent the coils from creating inductive kickbacks (http://www.allaboutcircuits.com/vol_3/chpt_3/9.html).



Also, it is possible that your supply is not stiff enough to handle the relay actuation current after you have a few on.
xxbaker  
#5 Posted : Tuesday, July 27, 2010 9:10:34 PM(UTC)
xxbaker

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Thanks for your help. I'm pretty sure the power supply is strong enough (it can run a few amps and the most I've measured the circuit drawing is less than an amp), but I suppose I could be wrong.

I do not have diodes across the coils - I did not know about that (first time really using relays). I ordered up some parts to try doing that.

In the mean time I tried wiring directly to the transformer and it would still freeze after switching relays on and off. Does this imply that it's because of an overtaxed transformer or could that still be because of the relay's inductive kickback?
xxbaker  
#6 Posted : Saturday, July 31, 2010 9:50:49 PM(UTC)
xxbaker

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Adding the diodes fixes the problem. Thanks again for the help.
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