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#58102 - 02/22/06 06:48 PM 990 with Niles AC-3 12V Trigger - no go!
buckeye1010 Offline
Deputy Gunslinger

Registered: 02/04/06
Posts: 5
I bought a nice Niles AC-3 box that switches a couple of 110V AC outlets on and off with a 12V DC trigger. I was going to use this for the built-in 110V AC fans in my rack. Well it turns out to not work with the Outlaw 990. The Niles requires 100mA, which is a bit high, but I thought the 990 could handle that. I measured 12V DC out of the Outlaw when switched on - so the Outlaw was working right. I found a 12V DC 90mA wall wart - it DID work with the Niles, so the Niles was working right. I just wish the Outlaw was spec'd in the manual for current output on the triggers.

I thought I'd share this experience with you all, so you didn't go through this.

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#58103 - 02/23/06 10:15 AM Re: 990 with Niles AC-3 12V Trigger - no go!
old_school Offline
Gunslinger

Registered: 09/24/03
Posts: 43
Loc: Ann Arbor, MI
One thing that you can do is to make a current driver of sorts. A friend of mine ran into this with another pre-pro (not the 990) in that even though the switched 12V was present when it should be, when connected to the projector, it would not trigger it (and the trigger voltage dropped to something like 3 V).

What I recommended to him was to use a simple BJT (bipolar junction transistor) as the current driver, mated to a wall wart for the actual operating current. It's pretty simple to build and works like gangbusters.

In essence, the 12 V trigger from the outlaw (which can't source much current (when loaded) as you have seen) drives the base of the transistor; the collector is tied off to the + voltage of the wall wart and the emitter then feeds the other trigger. Note that this can source MUCH more current because the Outlaw's trigger would only source enough current to drive the base of the transistor (enough to switch the transistor on).

Electrically speaking, looking into the base of a typical BJT it's probably somewhere around 1 M Ohm, so the Outlaw's trigger wwill remain very close to 12 V as it won't be pulled down by the load (it's like the transistor isn't even there, by contrast, the input Z of many trigger inputs is muc, much lower, causing the problem that you are seeing). Indeed, it's the wall wart that is sourcing the trigger current through the BJT and on to your connected triggers.

If you really want to make it ultra-low current (that is, the current required from the trigger output of the outlaw), use a Darlington pair (they are housed in one case so externally it looks like one transistor) instead of a single BJT. A Darlington pair transistor will have a HUGE Z looking into its base. This typically is not necessary, but in the case where the output Z of a trigger is really high, then the Darlington approach will almost certainly solve the problem due to its still-higher input Z than the base of a single BJT.

At any rate, this always works - the only limitation is that the wall wart be able to source enough current to drive whatever trigger input is connected to the transitor. So, just choose that wisely (and find one that's free of ripple, i.e. has some reasonable amount of capicitance).

Incidentally, you could easily source enough current for multiple devices' inputs (their triggers) by connecting them all to the emitter; again, the only real limitation here is how much current the wall wart will source.

Again, my friend did this with a Darlington NPN transistor that he purchased at Radio Shack.

I hope this helps - send me an e amil if you want further clarification.

Mark

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