Objective Development Forums

I have a couple 1N4729A 3.6V, 1W zener diodes. Will these work with a 20 MHz clock? I didn't even think about the low power requirement when I bought them.

Thanks,
Roger

Probably not. If you don't have the right zeners at hand, you may consider LEDs in series which have the same forward voltage drop as the zener would have.

Thanks Christian, I got EasyLogger working with a ATTINY45 and some diodes I salvaged.

can anyone take a look at the circuit of PowerSwitch? http://www.obdev.at/products/avrusb/powerswitch.html

I tried to change the circuit to run with red LEDs instead of Zeners.
I'm using an atmega8 controller running with 5V @ 16 Mhz (quarz).

Where do I have to place the LEDs to work in that circuit? Do I have to change the resistors from pull-up to pull-down and do I have to edit the code either?

thank you in advance,
bye

You replace the zeners with LEDs, no other change is required. However, you must use so many LEDs in series that the (measured) forward voltage is ~ 3.3 V. The LEDs must be in reverse direction compared to the zeners, since zeners have their breakdown voltage in reverse direction.

finally

I've tested it with two red LEDs in series from DATA+ to GND and two LEDs from DATA- to GND. That works fine.

The other solution was the method showed on the circuit of the USB-AVR home page with two normal diodes in series to reduce the voltage of the whole circuit to ~3.6 V.
http://www.obdev.at/Images/avrusb/circuit-zoomed.gif

My device didn't work earlier, because my hex-file was broken

thank you,
bye.