Thanks guys - lots of great ideas here.  It's good to hear that i'm not in as 
unique a situation as I feared... Time to play and see what I can let the smoke 
out of :)

Josh


--- In Repeater-Builder@yahoogroups.com, scom...@... wrote:
>
> 
> Hi Josh,
> 
> You can mod your Micor, but you'll keep running into similar problems when 
> you interface your controller with other repeaters. COR outputs can be driven 
> by Darlington transistors, LED drivers, squelch ICs, etc., and not all will 
> go as low as you want.
> 
> Here's how we've designed our controllers' COR, CTCSS, and logic inputs for 
> many years: Feed the COR signal to the top of a voltage divider. The upper 
> resistor is 10K and the lower is 4.7K. Feed the junction of the divider to 
> the base of an NPN such as a 2N3904, 2N2222, etc. You'll have a 3:1 voltage 
> divider that in essence multiplies the transistor's base-emitter drop by 
> three, so the input threshold will be ~2V instead of ~0.7V. And, you'll have 
> 10K and an NPN to buffer the outside world from whatever logic IC you're 
> using for your input port.
> 
> If you want a pullup resistor, tie a 4.7K from the top of the divider to +5V.
> 
> You'll find this circuit in all our schematics at www.scomcontrollers.com.
> 
> 73,
> 
> Bob
> 
> 
> 
> Bob Schmid, WA9FBO, Member
> S-COM, LLC
> PO Box 1546
> LaPorte, CO 80535-1546
> 970-416-6505 phone
> 970-419-3222 fax
> www.scomcontrollers.com
> 
> 
> 
> 
> -----Original Message-----
> From: Josh <josh.kit...@...>
> To: Repeater-Builder@yahoogroups.com
> Sent: Mon, Jun 21, 2010 9:57 am
> Subject: [Repeater-Builder] Micor COS issues.... continuing
> 
> 
>  
> 
> I've been fighting this issue for a while now. I've tried some bandaids to 
> deal with it, tried multiple repeater controllers (including one I designed 
> myself with an ATMEGA328 Microcontroller (I'll probably be releasing this 
> design as open source coming up)... and I'm fighting the same problem 
> everywhere... My micor COS signal is weird.
> 
> When the squelch is closed, I get right around 8 volts, taken from pin 8 of 
> the modified mobile audio/squelch board - the tried and true process just 
> about everybody uses..... When the squelch opens, I'm at not ground 
> potential, but right about half a volt. This isnt really the sort of logic 
> signal I want (I want this thing to be dead nuts zero, not half a volt). 
> 
> What is the deal here? 
> 
> I've tried adding resistors in series to fudge things and cause voltage drop, 
> but thats not really even working that well. I've tried the 2n2222 circuit, 
> but that doesnt really have a lot to do with this (although a variation of 
> that might come into play I suspect)
> 
> How do I best solve this so I can get my repeater on the air?? This is very 
> close to the last issue I have remaining to solve.
> 
> Help / advice is greatly appreciated.
> 
> Josh
>


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