Pin 39! [Vu]

22 Jan 2010

Is there a way to control this pin through code? im using this Carbon monoxide sensor that requires an oscillating 5v / 1.4v?

22 Jan 2010

Vu it is driven from the USB connector's VBUS (see schematics). So it only has power when you're connected to USB and you can't control it from software.

22 Jan 2010

I have used the alcohol sensor from sparkfun with the mbed no problems. Just attach 5V to the heater pin and use an analogin pin to read the values.


H and H -> Heater, heating pins for the sensor to work properly. Connecting to one another and GND VCC (5V)

A -> Pin sensor, connect to VCC

B -> Pin sensor, connect the mbed PIN, as well as a pulldown of 100K ~ 470K

27 Jan 2010

hey vlad, nice to know your looking over my shoulder :)

The CO2 sensor requires different interval of 5 and 1.4 V, something about cleansing the sensor or what not. take a quick look at the data sheet, but i did grab a methane sensor as well and working with that on the same premise of the alcohol sensor. Did you find that you needed to run the preheat time of 24 hours? otherwise my values are at about .99 and i should be evacuating my house!

28 Jan 2010

That happened to be as well but I just used a resistor to control my analog value scale. My prehead takes about 5 minutes after that the value gets stabilized. How have you been working out?

01 Feb 2010

Hey Vlad. Yup that's what i ended up doing, i forget what resistor i used but i think i kept going higer till my values were less sensative. Any workarounds for the oscilating value? Is there a way i could hook 2 pins in series to get my required voltage then just kill the one pin when it's not needed? (I come from a math/comp background, electrical is not my strong point )