LASER heater

[jimao22]

I wanna show you a small project of mine, completed these days. The winter is coming and dew and cold problems became annoying.

My problem was related on my 5 mW green laser pointer which I use it as a secondary finder, along with the 9x50 illuminated cross hair reticules finder scope on my telescope. As you know, perhaps, the green laser diode is very sensitive to cold and if temperatures drop down with the winter, the batteries are affected as well, so in 5 minutes the laser won’t work anymore.

I have an EQMOD controlled mount and I spend a lot of time in front of my laptop when observing and shot the stars, so is very useful to see where the laser beam point on the sky when aligning or synchronizing the mount with the planetarium. Of course, if I need more precision, I will use the finder scope or the eyepiece with illuminated reticule on the main telescope.

Anyway, the laser is very difficult to be used on the winter time. Until now...

[jimao22]

My solution is very inexpensive one. I used a nickel alloy wire 800W/220V, as those used for the electric heaters (sorry, I do not know the exact term in English) and a thermo-contractile plastic tube, used in electronics, big enough to introduce the spiral wire inside, as you see in the photo. The wire has a resistivity of 96-98 ohm. After insertion, I used a lighter to stretch the tube on the spiral and same time winding the result on one pencil.

The 2 heaters are identical as power but one was a little beat outstretched to cover a bigger area on the laser, where the batteries are.

[jimao22]

The heaters are connected parallel on 12 V and the final result you can see on the infrared pictures.

The small one have 53 degree Celsius on 23 degree on the air (indoor) and the bigger one , 42 degree.

Outside the values are 25 degree on -2 degree on the air for the small one and 17 degree to the bigger one. The power consumption is 3W for both and my field battery can supply power for 2 hours 20 minutes. When summer time and the need for high temperature is not so big, I can use the 9V output. In this case, the power drop down to 1.65W and the battery can supply power for 4 hours and 10 minutes.

In my test made last Friday, when I spent 9 hours outside (18:00 until 03:00), the laser worked amazing. The beam was so intense and no fades at all. I didn’t use the laser all the time and I disconnected the power when unnecessary but when start , it took just 5 minutes to be on full brightness again.

[Dude]

Wow... thats some high tech stuff you have there!

[Reggie]

That's very nice work Jimao22, the thermal images look excellent, definitely keeping it nice and warm

[yesyes]

Excellent idea. For a moment I thought you were going to connect it to 220V...

What did you use to get these thermal images?

[themos]

I'm thinking of doing the same but I was working under the assumption that the drop in temperature affects mainly the performance of the Ni-MH cells in the pointer and so I was thinking of just providing external power. Your setup can teach us about how the performance of the laser depends on the temperature of the laser diode itself. What is your view?

[yesyes]

good point.. does the laser diode need to be heated or only the batteries? the OP seems to imply that his laser is brighter when it's heated...

[jimao22]

The green laser have a resonator crystal and is sensitive to low temperatures.

The red one is different a beat. But the green is much more visible (more than 10 times) against the red one, because of the sensitivity of the human eye to green light.

So, the need to heat the laser diode is obvious. That's why I made the first resistor more "dense", to concentrate the heat around the crystal.

Anyway, the practice beat the theory and in this case, seems to be a good approach.

[Freff]

Great idea, well done.

I could do with the thermal imager to assess my observatory's warm room. See how much heat it's retaining/losing.