Beacon Keyer hardware

[syfr]

I've been playing with a Tiny85 as a beacon controller, due to its efficiencies

 I  lowered the clock speed to 1Mhz from 8. Nothing about a keyer needs 8Mhz clock.

I built an external high side switch circuit (2n3904 /  3906 pair) keyed from a digital output from the tiny to turn the 12v to the transmitter OFF when it's not actually sending something.  There's no use burning up power in the bias circuit if it's idle.

Transmitter runs off 12V, of course the Tiny needs 5. A  2950 regulator is fine for supplying the 5V.

I put the Tiny into SLEEP mode (there's some libraries out there on the web to do this. Not so many for the Tiny, but there are some) when it's not doing anything useful (between transmissions, etc). This keeps the Tiny running but shuts down most other functionality (inputs/outputs/DAQ's etc)  to save power. The transmitter is a Pixie (with no RX circuitry) and output is about 550 mW into 50 ohms.  I'm pretty sure I can do better than this by replacing the lossy molded inductors in the LP filter with small toroid versions.

Anyway, here's some supply current numbers with the results.   These numbers include the current to the ATTiny and the transmitter

Vcc 12.5

Icc (Transmitting) = 92 mA
Icc (Transmitter biased but not being keyed) 16mA
Icc (Transmitter disconnected , Tiny in sleep mode)  0.45 mA

That last number (0.45 mA for the whole system in sleep mode) is a nice one if battery capacity is of value to you.

If I recall correctly, the Arduino Nano pulls about 24 mA doing nothing, which is why I spent the time looking at the Attiny.  This is just a hint of a way to go that might help if you're looking to run off a battery.

Syfr

[Teotwaki]

bump for updates

[Quinta]

Tiny85 can be flashed from arduino ide, i made 2 beacons with tiny85, and use internal reference voltage for voltages measuring.