Optimod 2300 Tally Output to Sine RFC-1/B

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nickfish03
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Joined: Sat Jul 27, 2019 6:44 pm

Optimod 2300 Tally Output to Sine RFC-1/B

Post by nickfish03 » Tue Aug 27, 2019 7:47 am

Hello all, I'm new to the broadcast engineering field (and engineering in general). I installed a Optimod 2300 at our transmitter site this year, and recently hooked up two remote inputs so our Sine RFC-1/B remote control relays could switch the Optimod between Analog and Digital inputs.

Now, I'm hoping to take the two tally outputs on the Optimod to feed the telemetry inputs on the Sine remote for silence detection and input status.

I'm having some trouble understanding how to hook everything up. Am I correct in understanding the Optimod controls the Base of the Tally Output transistor and the Collector is already connected to Ground, and the physical tally pin is the Emitter? So according to the Sine Telemetry limitations, I either need to supply one to four volts DC, or use the Optimod's +12V pin, and reduce voltage before connecting to the Sine Telemetry connection?

Here's the information I have from the Optimod manual:
"In stereo encoder mode, the 2300 supports two hardware tally outputs, which are NPN open-collector and operate with respect to pin 1 (common). Therefore, the voltage applied to the load (such as a relay or opto-isolator) must be positive. You can use the 12 VDC source on pin 25 to drive the high side of the load, taking into account the fact that the voltage on pin 25 is current limited by a 310 Ω resistor."

From the Sine manual:
Telemetry samples should conform to the following rules:
• for a full scale voltage reading 1.0 volt DC is necessary
• telemetry samples over 4 volts DC should be dropped with an attenuator

DaveSt
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Re: Optimod 2300 Tally Output to Sine RFC-1/B

Post by DaveSt » Tue Aug 27, 2019 9:17 am

The NPN output transistor in the Optimod has its emitter connected to ground (pin 1). So you can use the collector which is the actual output to control anything so long as you stay within the current and voltage rating of the transistor. You can use a resistive potential divider so that you can pull up to the +12V output.

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radiowave911
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Re: Optimod 2300 Tally Output to Sine RFC-1/B

Post by radiowave911 » Wed Aug 28, 2019 4:33 pm

What I did for our Sine for this type of input is to use a 2 resistor divider. For this, probably a 10k and a 1k in series. The open end of the 10k connects to the supply voltage, the junction between the 10K and 1k to the sine input, and the open end of the 1k to the tally output. When the tally output goes low (I.E. the tally transistor turns on), current flows through the two resistors and voltage is seen across the two. Ignoring the voltage drop of the tally transistor junction, you would see about 1.2v between the junction of the two resistors and ground (the divider is a 10:1 - output is 1/10 of input). You might have to tweak the lower resistor a bit, depending on the voltage drop across the tally transistor, to get your 1.0V value. The current in this case should be somewhere in the neighborhood of 1mA, if I did my math right (it's been awhile since I did this :lol: ). I am quite sure someone will correct me if I am wrong. I thought I was wrong once, but I was mistaken....

I seem to recall that when setting the sine up for an 'On/Off' indication, there is a voltage threshold - anything above that is considered on, anything lower is considered off. I don't have my reference book handy at the moment to look, but something sticks in my head that the level is less than the full scale reading level.
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nickfish03
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Joined: Sat Jul 27, 2019 6:44 pm

Re: Optimod 2300 Tally Output to Sine RFC-1/B

Post by nickfish03 » Wed Sep 04, 2019 9:14 am

Ok, I see I was thinking about it backwards.
Thanks for the responses!
Nick

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