Power selector for Rkcstr?

Climber · Sep 23, 2009

I have a couple of questions about the Rkcstr driver. The Rkcstr driver has a bridge that selects a high/low output. I am thinking of building a laser that uses the bridge and a switch of some sort to give it a high/low power setting. I figure that if I have it set to the high setting to adjust the ma output while connected to a test load when the switch is changed to the low power mode the laser will work fine just not as bright. Any thoughts on if this will work or not? I have seen at least one commercially produced laser that had a power selector integrated with the lockout. If this works as I expect what would the expected ma that the switch would need to handle and would there be a problem if the switch is changed while the laser is on?

Glutton · Sep 23, 2009

I think you are confusing a test load with the driver itself. I do not think the rkcstr has any switches or bridges.

I recall someone talking about installing a switch with a test load in order to make the testing of blu and reds easier, but nothing like you are talking about.

Maybe I am wrong... the lava is kinda like you describe

Climber · Sep 23, 2009

I am talking about the switch being attached to the high/low bridge on the rkcstr driver to give it a high and low option. Switch closed would give a high power output and the switch open would be low.

The reference to the test load was to say that I am intending to set the power output while the driver is connected to the test load and switch set to the high power mode. That way when the switch is set to low it should be well within the power specs for the diode.

Sorry if I was confusing.

Glutton · Sep 23, 2009

Well if your idea only involves a mA adjustment, then it will work, just make sure that the voltage does not change...

Of course you will have to break the lase threshold of your diode and make sure that the high setting wont kill it.

Flaminpyro · Sep 23, 2009

Howdy Climber and welcome to the forum ! to answer your questions just about any small switch can handle the few miliamps it will see from the driver. and there should be no problem in switching it while the power is applied. as far as the current you will have to measure that your self I can't see it from here you are too far away LOL
I did something like what you are trying to do but I did it a different way as I built my own linear driver.
Best Regards Pyro...

Climber · Sep 23, 2009

Glutton said:
If course you will have to break the lase threshold of your diode and make sure that the high setting wont kill it.

I would set the power for the laser with the driver in the high mode so it should only go lower with the switch and then back up to the high setting. No changes to the output beyond what breaking that bridge causes.

Yes, the low may be too low to work depending on the diode but I think it may work. I will have to test it when I do the build.

Flaminpyro said:
just about any small switch can handle the few miliamps it will see from the driver. and there should be no problem in switching it while the power is applied

Thanks, that is what I was expecting. The low range is stated to be 30-57 miliamps and the high is 55-440. I would expect that the low range would be acceptable with the dial set for the high range although I do not know what the minimum power required for the diode.

daguin · Sep 23, 2009

Glutton said:
Well if your idea only involves a mA adjustment, then it will work, just make sure that the voltage does not change...
Of course you will have to break the lase threshold of your diode and make sure that the high setting wont kill it.

Just FYI

The Rkcstr now has a "switch" that can be used to make the driver a 30-58mW driver. The "switch" is a small trace that you cut. One COULD wire a switch to both sides of the cut trace and toggle back and forth. However, the low range is VERY low compared to where most diodes are run today.

Remember the pot is still active. If you have the pot turned down to ~200mA in high range, then the low range would be in the lower half of the 30-58mA lower range if you just switched it. Your laser current would be toggling between 200mA and 40mA

Peace,
dave

Glutton · Sep 23, 2009

hmmmm, interesting...

thanks dave:thanks:

Climber · Sep 23, 2009

daguin said:
One COULD wire a switch to both sides of the cut trace and toggle back and forth. Your laser current would be toggling between 200mA and 40mA

This is exactly what I am looking for. If I am playing with it and need the power it is there, but I also want a lower power mode for other times when I do not want or need the burning power.

daguin · Sep 23, 2009

Climber said:
This is exactly what I am looking for. If I am playing with it and need the power it is there, but I also want a lower power mode for other times when I do not want or need the burning power.

Those numbers are simply very rough mental estimates. :can: No actual math was done in this thread. :shhh:

Peace,
dave

Climber · Sep 23, 2009

I was referring to the concept not the numbers. As long as the diode can run properly off the low setting it sounds like everything will work as expected. My main concerns were how much power went through that bridge and if it would kill the diode if it was switched while powered on. Since both seem to be acceptable now this will be my first build and I expect it to go well. I have been reading the forums and checking the various sites linked for the parts for a couple of weeks. I guess it is time to order parts.

bryce007 · Sep 23, 2009

which diode you going to use it for? LOC? Although I only run them at 300mA, many run then successfully at around 420mA. So, if you turn the pot all the way up, your diode will see a max of 390mA - 400mA (IIRC), so you could just turn the pot to adjust the power instead of using the switch.

but PHR? Then it doesn't sound like a good idea to me

Mohrenberg · Sep 23, 2009

you could remove the resistor located under the pot, and wire in a switch with two different resistors.

but adjusting the pot would adjust both the high AND low setting at the same time. so you'd need to experiment and find two resistors that work well together, cause when you raise the pot, you'd raise the max current, but at the same time you'd be raising the minimum current.

HIMNL9 · Sep 23, 2009

Just add a trimmer and a switch (in series themselves) in parallel to the existing trimmer.

With switch opened, set the low power on the existing trimmer.

Check that the second trimmer is at maximum value, close the switch, and set it for the high power (without touch the first one)

Now you have a dual power driver, with both the levels at your desired power.

Can't say it more simple, sorry

(just be sure to use a switch that have sure contact, not a crappy one)

ElektroFreak · Sep 23, 2009

Climber said:
This is exactly what I am looking for. If I am playing with it and need the power it is there, but I also want a lower power mode for other times when I do not want or need the burning power.

FYI, switching a diode that runs at 200mA to 40mA will likely not even be enough to bring the diode over it's threshold (so no lasing). You'll be switching it between high and off. You'll already have a switch for that. HIMNL9s advice above will circumvent this problem, but will add bulk to your driver (although whether that matters or not depends on the installation).

Mohrenberg · Sep 23, 2009

this sounds like a pretty fun project....make a labby in a project box, and have like the top of a project box with a main on/off switch, and then have it lined with switches that increase the current by 50mA or so lol

use a rkcstr fixed output driver (if ryan has any left) and wire in one 25.5ohm resistor to each switch, then each switch that you turn on increases the current by 50mA

11 switches haha
main on/off
then 10 more switches that can bring it to 50,100,150,200,250,300,350,400,450,500mA

this would work good for graphing diodes too.....

Power selector for Rkcstr?

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