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FrozenGate by Avery

Temp sensor and safety switch

TacoHerder

TacoHerder

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Ive been thinking how nice it would be to make a laser that has a safety switch of some type and maybe a temp sensor in case your heatsink starts getting overheated. Anyone know where i could find something like that? Been looking, so far cant find anything small enough to place in a laser host.
 





rhd said:
Unless you want to reinvent the wheel (or rather, the driver), why not just create a circuit that the power flows through prior to the driver? Then have it open the circuit when a thermistor registers above a particular temperature?
Click to expand...


I was thinking about that. If my switch had an LED light, would that throw off the power leading to the driver? Or should a low voltage LED switch work? I guess then i need to make sure my host has room for the extra internal circuit.


bad thing is im not skilled enough yet to make a circuit for the switch :(


I found a lot of temp sensors and stuff on Digikey.com. Now i just need to figure out what i can and cant use.
 
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The main problem is fitting it all in to the damn host, haha. I can whip up a circuit to shut off power above a certain temp pretty easily, but getting it made and made to fit inside a tiny host.... yeah total nightmare. The simplest circuit is still going to need a transistor (mosfet) that can handle the power being drawn by your driver, and usually this means the transistor needs to be heatsinked, compounding the issue.

Building a thermally protected labby? No problem. Building a thermally protected handheld? Ugh.

Just my $0.02
 
Yup, i come back to that conclusion every other minute. It would be so nice though. How does WL have their safety swith set up? Unless they skip the heatsinking part.
 
IIRC they have a thermistor on their driver which controls analog modulation (reduction of power at increased temperature). As RHD said, "reinvent the driver". It's a lot simpler than APC driver topology, and those have been around since the early nineties, if not earlier.

Any driver with analog modulation built in can be converted to automatic temperature control by simply forming a voltage divider with a thermistor.
 
The simplest option would be to simply use a thermal switch in series with the driver input. Something like this.
 
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Cyparagon said:
The simplest option would be to simply use a thermal switch in series with the driver input. Something like this.
Click to expand...
MAN! Thanks for that. Looks like a very simple solution to helping protect the diode from excess heat and neglected use(not that i plan on doing any). When i build my next 445nm i want to give this sucker a try.
 
Sigurthr said:
Any driver with analog modulation built in can be converted to automatic temperature control by simply forming a voltage divider with a thermistor.
Click to expand...

I suppose this would also work on a drive with an enable pin, as long as it has some hysteresis. Downside is that it will shut off abruptly, and may take some time to cool down enough before it turns on again.

I've never tried it myself, but it would be a good method of making a portable laser foolproof in terms of duty cycle.
 
Cyparagon said:
The simplest option would be to simply use a thermal switch in series with the driver input. Something like this.
Click to expand...

So i got a few of these to try out whenever i build my next strong laser. Do i have to put this before the driver, or can it be placed between the driver and diode?
 
^^ definitely! Otherwise the diode could fry when it re-engages and suddently connects the laser back to the driver which is supllying maximum voltage at that point (and charges its outputs caps to the max if it has any).
 
Wow, ya im trying to avoid stuff like that. Thanks a lot guys. Ill most likely be using this before my dual drivers or a linear driver. Im not even sure how to go about putting this in front of a round driver.
 
i too am working on something like this. i believe zener diodes have a point at which they let current flow, if that is correct, you could simply hook a thermistor to a low current zener and to power supply, then have the zener switch a lower power fet, just enough to light an led from the power. you wouldnt have to worry about heatsinking the fet that way. but you would have to switch off the power manually when the led comes on
 
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