I have a 3.3v board, and an RF transmitter that can handle up to ~12v. Assuming I want to power the transmitter with 12V for the range but use the 3.3v signal coming from the board's IO for data, can an optocoupler be used to run these two devices? Can it keep up with whatever the data is like for 433MHz ASK?
Yes - but a simple transistor would do quite as well
regards
Allan
Just because the transmitter can handle up to 12 volts does not mean that the I/O has to be (or even should be) 12 volts.
More information is needed (e.g. data sheet, model number, link).
Optocouplers I have have a rise and fall time in the park of 5microseconds ea. Is this enough to throw off RF ASK or do the delays just basically cancel each other out?
The signal you are passing through the opto is not RF the fact you have an RF transmitter on the output end has no baring on the situation. The MIDI speed of 31,000 (ish ) baud is a fast speed for an opto coupler and some types will not cope with it.
No the delays will not cancel each other out and you need carful design to a achieve what the data sheet says you can get.
There are fast opto-couplers designed for logic signals and supporting baud rates of 5M or so, but
they are more expensive and require logic power on the receiving side. For instance the ASCL6400 family.
There are also non-opto isolated logic couplers now that use capacitive coupling on a GHz carrier,
these handle 10MHz or so logic rates and use less power than most opto-couplers.
Are you talking power supplies or input signal voltages?
Just because the transmitter can accept voltages from 5-12v doesn't mean it will transmit with more power at 12v over 5.5V if you are talking power supply. It all depends on what the power is regulated down to at the transmitter. The input signal from the 3v board may fall right in line with min/max input signal voltages.
Using efficient antennas placed in ideal locations may be the best way to extend ranges.
No power regulation on the transmitter module.
I was hoping someone familiar with the 433MHz ASK/OOK timing of the highs/lows could chime in, but I found a vid of someone reading the signal through a sound card and it seems shorts are ~400microseconds and longs about 3 times that. The rise/fall time of optocoupler is within the margins of recognition.
Stacked 4 coin cells for 12V, transmitter is working through the optocoupler.
Going to keep using it to see if it drops any transmissions, but it's been 100% so far.
Once it stops raining I will run it out to see if any distance is gained over the 200m range @ 5V.
So my wiring, for anyone interested
Arduino side of optocoupler:
Data out pin to optocoupler anode, optocoupler cathode to Arduino GND through a 330ohm resistor (opto's internal led is 1.2Vf, giving it ~13mA)
Transmitter side of optocoupler:
VCC and GND to battery + and -, respectively. VCC to opto collector, opto emitter to DATA pin.