Timer for Duty Cycle

[pschlosser]

confidence is what I want. confidence that if I loan my lasers to a responsible party, such as my older brother, I don't need to worry he'll exceed the duty times. he went camping with his girlfriend. he took two lasers, a greenie and my new blue 445nm by Blord. (yes, and goggles, too) I worried all weekend he might cook one. The more I pay for a build, the more I'd like the confidence it's gonna last by not exceeding duty cycles. Were the duty cycle enforced by a circuit, then I could worry much less.

There is a great deal to think about, when operating a laser. why make it more complicated if a circuit could deal with one of the parameters (duty times)?

Even I have lost track of time chasing an ant across my wall. "will you just hold still!"

 

[Fracker]

Lemme see what I can scrounge up tonight. I have untold amounts of timers and various electrical controls. there are solid state timers that will run on line voltage and there's a 555 timer ic that is the mainstay for ic timers. I know expense is an issue but you also don't want it to stop during a show. I'm sure there's 20 different ways to do it. I'll get back to you later tonight after I have some time to find what I'm looking for. The best part is If I find something ill just send it to you free to try out. Then you won't have to spend any money to try it out and see if it's viable for you.

 

[pschlosser]

Lemme see what I can scrounge up tonight. I have untold amounts of timers and various electrical controls. there are solid state timers that will run on line voltage and there's a 555 timer ic that is the mainstay for ic timers. I know expense is an issue but you also don't want it to stop during a show. I'm sure there's 20 different ways to do it. I'll get back to you later tonight after I have some time to find what I'm looking for. The best part is If I find something ill just send it to you free to try out. Then you won't have to spend any money to try it out and see if it's viable for you.

Thank you. But you need not send me anything. This is more of an exploration than a need.

I think space is more of an issue than expense. Because I would, as may others, want these circuits to be included in laser pointers where we are really pushing the limits of the diode. And, yes, I want to to shut off, or throttle back the current to 25% or something safe enough to protect the diode, were the operator to keep the device powered.

Further, a laser I may be using in a show, will not likely be a laser pointer, but a lab laser. And in a lab laser, I've already resolved heat sinking to a degree that I need not bother with duty times. The circuit I have in mind is small enough to be included with the driver inside the laser pointer, if even possible, and configurable to some degree by selecting the right components during assembly.

 

[jArdi]

it'd be better to use a thermister to gauge the temperature of the diode. Use that along with a pot, a relay, and some other componenets, and you have a simple circuit that can disconnect power to your driver when the temperature gets too high.

I have a suggestion. Why not use a driver with TTL input and then drive that at 5V with a PWM. You can set the duty cycle to whatever you like, then adjust the frequency to get a pleasant strobe-like effect. Fast enough pulsing will appear to be on constantly, albeit at a lower average power.
Bob

The BEST thing you can do is combine these two ideas - and i know it WILL work because I've done it before; just not with a laser and for the purpose of duty cycle, but its the same concept exactly.
What you can use is an ATtiny45 or an ATtiny85 (if you need more memory) microcontroller - there only about $1 each online.
It has 6 I/O lines so you can attach a thermistor, a relay, maybe a button and an led if you like, anything you want

If you want to go with the bare minimum and have it go on every x seconds and off every n seconds, all you will need is one of the ICs, and a transistor. A decoupling capacitor along power rails would be smart (and safe) though. I would highly encourage you to do this because its a very reliable chip and has endless limits to it.

Link to ATtiny45:
ATtiny45
Link to ATtiny85:
ATtiny85

if you are going to buy them, i would suggest using newark. they are very fast at shipping and you will likely receive it sometime the same week.
If you are on a limited budget, then you can always find places online to order free samples from. i forget where, but I ordered 5 surface mount and 5 through hole and received them the following week - for NO cost. free shipping and everything

If you need help with this, pm me and I would be happy to help you

there are solid state timers that will run on line voltage and there's a 555 timer ic that is the mainstay for ic timers. I know expense is an issue but you also don't want it to stop during a show

if you dont feel like coding or using an AVR, this is probably the next best thing you can do, except it will take up much more room. depending on the mode you are using, you'll probably need 1 or 2 resistors, a capacitor, and of course the chip and a transistor. The parts will be available at your local radioshack (i hate their timers though - always horrible luck with them) and shouldnt be more then a couple of bucks (online you'll probably find them for 1/4 the price because radioshack like to charge you $2 for $0.02 caps parts)

i can help you with this too if you need, but i would still suggest using the ATtiny. If you want, you can even make different modes with the ATtiny though

PM me if you need help - good luck!

 

[Fracker]

Thank you. But you need not send me anything. This is more of an exploration than a need.

I think space is more of an issue than expense. Because I would, as may others, want these circuits to be included in laser pointers where we are really pushing the limits of the diode. And, yes, I want to to shut off, or throttle back the current to 25% or something safe enough to protect the diode, were the operator to keep the device powered.

Further, a laser I may be using in a show, will not likely be a laser pointer, but a lab laser. And in a lab laser, I've already resolved heat sinking to a degree that I need not bother with duty times. The circuit I have in mind is small enough to be included with the driver inside the laser pointer, if even possible, and configurable to some degree by selecting the right components during assembly.

That's cool man. That offer was mostly for MC77 as his request was more towards what I was offering. I should have stated that in my post.

I do agree with you though. I am sure with today's surface mount technology that someone could incorporate a cycle timer or automatic current reduction right onto the driver board that uses very little space. That would be awesome.

 

[M7CC]

Appreciate that Fracker. I ordered the timer (from my earlier post) but after reading through the other responses, I'm not as worried. I'm not using a very high powered module and there will be a fair amount of metal around it.

Again I'm just looking to set up a nice hands-free liquid sky effect in a small room. I'll see how long this laser runs before it gets hot (if it does) and then try the timer if I need to.

If I get more into this I'll look into the thermistor/TTL idea. I went ahead and ordered this as well, by the way:

Intelligent Temperature Control Module Thermometer LED Display DS18B20 Sensor | eBay

Don't know if the provided sensor could be placed near enough to the heat source to be effective in this situation or not. It could come in useful for other projects though. (Sorry I hate when people post eBay links on forums as they have very short lifespans. I couldn't find these anywhere else though.)