monitoring the status of another system

[mikeleslie]

I am trying to monitor the status of another system (a rather complicated battery charger in this case) using my Teensy 3.1. The system has about 10 LED's (green, yellow or red) that indicate various states. The system is mounted in such a way that I can't see the LED's while it's operating. I was thinking of using a photoresistor and just filtering for the red (I only care about the red) but this just seems a little too simple. I am thinking of it more or less like a color detector, I'm just not emitting the colors. while operating, there isn't any ambient light to mess things up.

any thoughts as to whether this is a reliable approach or if there is a better approach would be appreciated.

The whole thing is complicated by the fact that I don't have access to the equipment (until I install it) combined with it's remote location means that I have to have the hardware right before I go install it. Software I can change on site.

Thanks, Mike

 

[Xenoamor]

I assume you don't have the option to just tap onto the LED drive line?

The method to colour detect is your only option. Either that or cover up the other LEDs.
If there's no ambient light this would work very well and you could implement very crude detection logic

 

[mikeleslie]

Unfortunately I can't tap in.
I hadn't thought of just masking (at least from the sensor) the ones I don't care about. That would certainly make the detection logic simple as well...."If you see light there must be an error"...even I can code that!

Thanks

 

[pictographer]

You might consider photodiodes, phototransistors and PIN diodes. Different light sensors have different response times and response curves to differing wavelengths of light.

Photoresistors respond relatively slowly and have output that is relatively noisy. If you buy from a major electronics distributor, you can search for devices that are most sensitive to the wavelengths you care about and you can study the data sheets in advance.

I recently put together a little light monitoring system that I'm very happy with for monitoring sunlight. The intent of the system is to provide a way to monitor my solar panels that's independent of the PV system.

The rig consists of a TP-Link TL-MR3020 wireless router running OpenWrt Linux in client mode with a Teensy 3.1 connected to its USB port. The Teensy has a photodiode connecting two pins. The router is powered by a USB power supply.

To Linux, the Teensy appears as a serial device that periodically reports the output of analogRead(). I haven't finished the software that timestamps the readings and compares them to the output of the PV monitor. The PV system already logs its production to a Linux server. The OpenWrt device will log its readings to the server as well.

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