Reading the intensity of an IR Led using a PNA4601M IR Receiver

That component is intended to work with a 38 KHz modulated signal. It has an internal bandpass filter in order to reduce the sensitivity of the device to constant sources -- like your IR LED. If you hold a typical IR remote control up to it and trigger the remote with a repeating signal (like, say, volume down) then you should see a net deflection with your multimeter. This

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And shame on Parallax for not providing a link to a datasheet!

You want to look for a plain old IR phototransistor or photodiode. A phototransistor is probably more what you want (it'll have better gain).

Don't get the floor-sweepings that Radio Shack sells unless your needs are very modest -- go shopping at DigiKey or Mouser and get something that doesn't need to be pounded with light to detect something.

"BurningFuses"

BTW: Do you think "steak sauce" is made from steak?

... Phil

Actually Parallax does provide datasheets along with an application note and a sample BASIC Stamp project. These are under the download section of the location given by the OP.

Dan

Streak cameras are for photographing naked people running around.

ight.

om/product/350-00014) that I bought from Parallax a while ago.

e GND and read the voltage out through the Vout. The higher the voltage, th e stronger the IR Light shinning on the IR Receiver. But that is not what h appened.

Vout), I get 5V (a bit lower than the input), even with the IR Led turned o ff.

My favorite way for detecting light is to stick a photodiode across the uA current input leads on my DMM. Bang you're done.. and if you know the wave length then you have a decent measure of the light intensity. (Assuming acc ess to the photodiode data sheet.)

George H.

For low levels, use the voltage leads. A 10 meg input impedance voltmeter is an ammeter with sensitivity of 100 pA per millivolt. Even cheap meters can reliably measure nanoamp currents.

e light.

x.com/product/350-00014) that I bought from Parallax a while ago.

the GND and read the voltage out through the Vout. The higher the voltage, the stronger the IR Light shinning on the IR Receiver. But that is not wha t happened.

uA current input leads on my DMM. Bang you're done.. and if you know the w avelength then you have a decent measure of the light intensity. (Assuming access to the photodiode data sheet.)

is an

eliably

OK.. I guess that's for *really* low light levels! I futzed around to get 1uA of photocurrent...(Pretty dark.) On the volt/ milli volt scale this re gistered as ~200mV... (One might worry about the input impedance of the meter on the milli-volt s cale... I know some go into a high Zin mode.)

So the diode had an resistance of ~200k ohm... Hmm why not 25mV/1uA = 25k ohm? (I seem to be confusing myself.) Yeah, I know, with light shinning on it t he I-V curve is displaced downwards. I tried a smaller area PD.. more light for 1uA.. and now that gives 230mV i n voltage mode. (scratch scratch...time for lunch.)

George H.

Most stay at 10M, although some bench meters can optionally go hi-z. A bigger issue is that, if you want to measure diode current in PV mode, you need the voltage to be low, probably no more than 100-200 mV maybe. At higher voltage, the diode conducts and gobbles up its own current.

Use the current range if it has enough resolution.

get 1uA of photocurrent...(Pretty dark.) On the volt/ milli volt scale this registered as ~200mV...

t scale... I know some go into a high Zin mode.)

OK this is nice.. here?s the forward voltage drop vs bias current. Vf is for the PD I used yesterday ~200mV at 1 uA. The PIN-44 is one we com monly use...about the same area (for comparison.) There?s something like 100 ohms of resistance in series with the diode drop... but it?s non-lin ear. (less resistance at 10mA)

For these PD?s you?ve got to be below ~100mV to not have any current su cked up by the diode. But for low light levels you could just use the loga rithmic behavior of V to get an estimate of the light intensity. (You?d have to do the I-V of ?your? PD first.)

George H.