LED light thermal protection with thermocouple

Hello, I am working on designing my first arduino project. The goal is to protect my LED light bank from failure by using a thermocouple wire > maxwell6675 > arduino > power relay.

I already have the LED light built, it is using Cree CXB3590 COB lights. They are expensive and if they run too hot (because air conditioner breaks) then the arduino will kill the power to the light bank until the AC is repaired.

Please see the sketch attached to this post for my design.

Parts I think I need for the project:

1 x arduino mega
5 x max6675 thermocouple sensor
5 x 0.1uf caps for fixing line noise on maxwell6675s
5 x thermocouple wire
1 x Arctic Silver Arctic Alumina 5g Premium Ceramic Thermal Cooling Adhesive Set
1 x 5v one channel high power relay for switching off LED power.
??1 x 5v power supply that will have adequately power all the max 6675??

Will this design work? Since all the max6675 devices need 5v power, what is the best component I need to power all these devices simultaneously without putting a strain on all of them?

The cree chips have a thermocouple contact point… it is too small to solder onto so I will just use the ceramic adhesive which is what Cree LED and other LED manufacturers recommend. I realize that the reading will not be 100% accurate, that is OK. I will be able to “calibrate” it with a true handheld thermocouple temperature meter to make sure my arduino readings are relatively accurate.

Thanks for any feedback you may offer.

0.5_caps.png

5v1ChannelRelay.jpg

ArduinoMega.jpg

CXB3590_med.jpg

A digital temperature sensor would be a far more appropriate sensor for this task.

Paul__B: A digital temperature sensor would be a far more appropriate sensor for this task.

Yes, you can use One Wire Digital Temperature Sensor - DS18B20 Measures temperatures from –55°C to +125°C (–67°F to +257°F) |500x500

Since Cree CXB3590 COB lights is best operate at 85°C, so DS18B20 more appropriate and less parts for youe project.

BillHo:
Yes, you can use One Wire Digital Temperature Sensor - DS18B20
Measures temperatures from –55°C to +125°C (–67°F to +257°F)

Since Cree CXB3590 COB lights is best operate at 85°C, so DS18B20 more appropriate and less parts for youe project.

Thanks so much. So I would just epoxy the digital sensor directly onto the ceramic LED plate so it is in direct contact with the LED (and not measuring ambient air?

thanks so much BillHo and Paul__B :slight_smile: really appreciate the fast advice

Are your lights mounted on a heat sink like this? https://www.thcfarmer.com/community/threads/my-plan-for-a-cree-cxb3590-light-bar.72868/

mikb55: Are your lights mounted on a heat sink like this? https://www.thcfarmer.com/community/threads/my-plan-for-a-cree-cxb3590-light-bar.72868/

The LEDs are mounted directly on aluminum heatsink inside an IDEAL COB holder. There is no fan, it is using passive cooling. The LED has a thermocouple point that can be soldered to to get accurate temperatures. Can the digital DS18B20 chip be expoxied directly to the cob? Or will the epoxy throw off the reading a lot? Here are pictures:

Glue may work. Personally I would use a scrap piece of fibreglass PCB screwed down to the heatsink so that the sensor is pressed against the thing being monitored. It would make it easier for maintenance.

Instead of completely turning off the light, you could use PWM to lower the brightness when the temperature rises above some alarm threshold. Once triggered you could wait for some period of time before setting the light back to full brightness.

mikb55: Glue may work. Personally I would use a scrap piece of fibreglass PCB screwed down to the heatsink so that the sensor is pressed against the thing being monitored. It would make it easier for maintenance.

Instead of completely turning off the light, you could use PWM to lower the brightness when the temperature rises above some alarm threshold. Once triggered you could wait for some period of time before setting the light back to full brightness.

ok great ideas thanks guys!

Or you can get the sensor in this packaging, make it easy to fix it in place.

Waterproof DS18B20 Digital temperature sensor

Hi, It looks like your heatsink is just a piece of aluminium channel. You would be better off putting a finned heatsink in the channel as well to move the heat. Does the COB holder specify any heatsink requirements?

Tom.. :)