Ir and photodiode confusiom

[DJSterrett]

Working with an Arduino Nano pro. I have a shield that just allows an external power supply and adds screw terminals to the pins. Using a fairly simple sketch that only relies on a photodiode and an IR led. When I put the Led(with resitor...200ohms) and the protodiode directly into the proper terminals​ the program works flawlessly.(this is how I tested the program for students) When the same components are wired with 3ft of wire (we want to attach these to something)...there is no output to the program...at first I thought it was a wiring error, but myself and 4 students took a crack at it and no joy. But then you take the same components and hook them back up directly...program has flawless out put again. What are we missing?

[groundFungus]

We can't see what you are doing.

Please post a schematic showing how the wiring should be.

Post clear photos showing how the wiring is. Then maybe we can help without just making a bunch of guesses.

Technical data (data sheets) for the relevant components can also be helpful.

[EmilyJane]

3ft of wire might be too much impedance for unbuffered outputs. While you're doing what @groundFungus suggests you might also take a look at both ends of the connections if you have access to an o'scope. Tell us what kind of wire you're using and how you are powering the project.

[dlloyd]

The photodiode is very sensitive and needs to remain close to its amplifier. Perhaps a photodiode module would be more suitable for use with an extended cable, rather than modifying a shield type circuit.

[DJSterrett]

Will have to wait on actual wiring pic...its at work....22ga stranded wire

[dlloyd]

Since there's no amplifier for the photodiode, it would be better to use a phototransistor instead.
Currently, the cable to the photodiode would act as an antennae and there won't be enough signal strength to detect anything meaningful.

[johnerrington]

Using Operational Amplifiers in your Arduino project

4: Using Op Amps: A Practical example Measuring light level with a photodiode Photodiodes are used in many every day electronic devices such as cameras, smoke detectors, burglar alarms, safety equipment, medical applications, CD players and surveying instruments. They can be used to detect a wide range of electromagnetic radiation, from infra-red through the visible to ultraviolet and even x-rays. They aren't just for visible light. How they work When a photon (a bit of light or other EM wav…

Thanks for trying with a schematic - sadly its too small for me to see what pins you are using.

How to make a schematic you can post.

When you submit a question on the forum you will usually need to add a schematic (circuit diagram). The tutorial that follows will explain some ways to create a useful image; however lets start by explaining how to add the image to your post. Its easy. Having created the image all you need to do is : Save the image somewhere convenient - maybe your desktop Start your post, and place the cursor (insertion point) where you want the image to be shown; [upload image to forum] 3: click th…

@DJSterrett

Using a fairly simple sketch

Can you post it please?

[jremington]

@DJSterrett

When the same components are wired with 3ft of wire

Use your multimeter to check continuity of all connections.

[mrburnette]

My vote is that Emilyjane is on track:

The photodiode's cathode goes directly to the Arduino input pin. Long lengths of unshielded/untwisted wire will have AC hum influence and if around florescent lighting (example) will overwhelm the Arduino input.

[EmilyJane]

We haven’t seen any code either so it’s not known how OP is treating the output from the photodiode.
@johnerrington ’s suggestion for a buffer would work if you put it on the photodiode end. Otherwise it would just amplify the problem.

[johnerrington]

It would make sense to use shielded twisted pair cable to make the connection as the diode will rectify any pickup.

However I'd be VERY surprised if 1 metre of wire picked up any serious signal unless in a really high field environment.

I have experienced a situation where the earth conductor (20m vertical wire to an earth spike) picked up 70V of HF - when a nearby microwave heater was turned on!

[DJSterrett]

Solved the problem...was the carrier I put the emitter and receiver in

[johnerrington]

just for completeness @DJSterrett can you provide more details?

[DJSterrett]

So...I've tried to explain it in the picture...if I set them up non parallel and not contained in the holder it works