[aprssig] Tracker3 OT3m

Scott Miller scott at opentrac.org
Fri Jan 6 11:52:08 CST 2012

> 1. How much current can the 5 VDC pin on the accessory connector supply?

It's going to depend on how it's powered.  Not more than half an amp, 
which is the most the regulator can handle.

> 2. How are the analog inputs scaled? You say that initially they are
> scaled for 0-20 volts. If I have a pressure transmitter with a range of
> 0-5 inches of water column which equals 0-5 volts, do I simply scale
> that input in the OT3m as if it was 0-20 inches?

They've got voltage dividers that allow them to read up to 4x Vdd - 
which will actually be a bit less than 5v because of a Schottky diode 
drop, so realistically the limit will be about 19v.  Regardless, the 
telemetry values are given in tenths of a volt - e.g., 123 = 12.3v. 
It's got a 12-bit ADC and could be configured differently for different 
applications, but for now that's the default.

> 3. Is the counter input looking for a contact closure or a voltage
> pulse? Same question for the digital input.

Contact closure, and I'll have to check if the internal pull-up is 
enabled on the digital input or not.

> 4. Where is the voltage source for the Power Switch Output come from?
> Doesn't the power control feature on OT2m switch a voltage source that's
> completely separate from the tracker power supply?

The OT2m's source isn't separate from the power supply, but it has big 
pads very close to the switch.  The OT3m will switch power from the 
radio connector or the power jack.

> 5. What is the part number for the accessory connector? Will you be
> selling that connector separately?

It's a standard 0.150" pitch terminal block.  I'll list them separately.

> 6. I am not very familiar with APRS telemetry, so this may be a dumb
> question...Can the sequence number (T#sss) be reset back to 0?

You could reset the whole tracker, and it also restarts on power-up, but 
so far no one has ever requested a manual reset function.

I'll try to get all of this into the wiki.


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