Pulse IR
- Thread starter borz
- Start date
Michael 2727
Senior Member
PWM Pos+ = Supply Voltage POS+.
Standard practice is a 330 Ohm (LED) Resistor for most supplies 3V to 5.5V
If you want to get into the nitty gritty of things and get the Max from
your setup use- Supply V ?, minus LED forward V drop ?, at 20mA.
Standard practice- Don't drive any Picaxe output at more than 20mA.
If your IR LED is capable of 50mA pulses or 100mA @ %10 Duty, then
you need to use a Transistor/MOSFET driven from the PWM output.
BTW the 940nanometers is the spectral wavelength of the IR light
produced, not really used in electrical terms.
You only need the Vf (voltage forward drop ) and the 20mA (typ) and
maybe the IF-max (Continuous Forward Current-MAX) if you want to drive the unit pulsed/hard.
Standard practice is a 330 Ohm (LED) Resistor for most supplies 3V to 5.5V
If you want to get into the nitty gritty of things and get the Max from
your setup use- Supply V ?, minus LED forward V drop ?, at 20mA.
Standard practice- Don't drive any Picaxe output at more than 20mA.
If your IR LED is capable of 50mA pulses or 100mA @ %10 Duty, then
you need to use a Transistor/MOSFET driven from the PWM output.
BTW the 940nanometers is the spectral wavelength of the IR light
produced, not really used in electrical terms.
You only need the Vf (voltage forward drop ) and the 20mA (typ) and
maybe the IF-max (Continuous Forward Current-MAX) if you want to drive the unit pulsed/hard.
Last edited:
Comparison of Input and Output [I/O] logic switching levels for the CMOS, TTL, mixed CMOS/TTL, ETL, BTL, GTL.
http://www.interfacebus.com/voltage_threshold.html
http://www.interfacebus.com/voltage_threshold.html
Thats handy bg, but does Borz know which one he's meant to be looking at?
Mayb you could tell him.
To Borz: use Michael's suggestion of a transistor. It is the only way can you can give the IR LED some real ooomph.
Note: If you want longer ranges you can usually give IRLEDs a lot more oomph when pulsing, some can be in the amps for brief pulses - sadly you would have to read the device Data Sheet looking at peak currents, duty cycles and derating.
Mayb you could tell him.
To Borz: use Michael's suggestion of a transistor. It is the only way can you can give the IR LED some real ooomph.
Note: If you want longer ranges you can usually give IRLEDs a lot more oomph when pulsing, some can be in the amps for brief pulses - sadly you would have to read the device Data Sheet looking at peak currents, duty cycles and derating.