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Agreed. I forgot to mention this and it is important. If there is an over spec on the Flexmod, it is this 25W dissipation value. This driver drops 1.5 V internally and so you need to exceed your minimum voltage output by at least this amount, but by as little more as possible. at a few amps and a few volts of drop, the unit does become HOT!Quote:
recommend is keeping the voltage drop the driver has to deal with as low as possible
Hi Draco,
My last drivers with the OpAmp current-regulating were for a special project with NDA's, so not free.Quote:
Originally Posted by Draco
My first drivers with LM317 and LM338 were stable too and they are free ;)
Here are some older infos about the diodes - http://www.reprap.org/wiki/Laser_Cutter
Attached is a simple schematic of a 5A-driver ... I've used this type with a single LM for 500mA-Diodes, of with up to 5 LM338 for 12A, but could parallelize even more for any needed current. For faster switching I've replaced the opto-coupler with an 6N137 ... it's only needed for switching with different voltage levels than 5V ...
Viktor
Thank you very much for the info, looking at the schematic, K4-K9 select the max current with a jumper, K1 is power in and K2 is the analog or pwm modulation? K8 enables the FET if jumper-ed pin 1 and 2, and in cut off with 2 and 3?
Thank you for the link as well, i have a 20 watt fiber coupled diode bar that i have wanted to use in a project like an engraver or cutter. What i like about this is it seems to be simple and easy to scale up or down
... yes, the numbers are correct - I've installed the K8 for safety reasons (simplest safety circuit) and when configuring the sense-resistors for 'odd' powers, then you can combine the max power with finer steps (did this sometimes with 0.1A, 0.5A, 1A, 2A and 2.7A) and set/activate them with relays and a controller per software ;)
Viktor
my luck just gets better and better, while i was measuring voltages and tracing paths on my good P3.3 i forgot the laser diode was connected and blew the diode, note to all, use a dummy load or an LED while doing these types of tests and USE a Lasorb! the P3.3 has a protection diode and the diode "has" ESD protection on the device it's self but this was not enough, i think i would be better off to go down to the local tavern and pay some one 35 bucks to beat me up, at lest i would have some bruises to remind me of stupid actions then just another shorted laser diode. :mad:
on a plus i do know my failed P3.3 is driving the FET into saturation and the FET is not the device at fault
I'm with you there. The only time I have a laser diode hooked to any of my drivers is AFTER everything is hardwired and the pots are set with a dab of adhesive. Otherwise, I always use a junky 3W LED for my tester load.
when did I say that? all I said was using a bench supply in a projector that is actually used for shows is sillyQuote:
Originally Posted by Draco
you could use a current limiting DC-DC converter if you really wanted to, or you know, just fuse properly ;)
The problem with just using a fuse as a current limit would be the final part in the chain, the flexmod p3.3 has a built in fuse at 4 amps if i remember right. I like the idea of using the lm317 as a current limit, they will generate some heat and i think thats the direction i will go when i am using a power supply other then my bench supplies. and there are a lot of people that use bench supplies when they are working on or prototyping their projectors. fuses as a measure to protect the diode won't reliably work, they are too slow but can prevent the driver from catching fire or damaging the supply that would be used with the projector when at a show.
I have the blue laser up and running again thanks to DTR's fast shipping and with the failed p3.3 there are two devices i am not able to identify, 2 of the unknowns are a 5 legged ic, one of which directly drives the output fet, they have a house marking and i can't find any correlating data on what they are. my theory was the one 5 legged ic was a current sense device but the voltages dont match the device i thought it was.
I still have not had any reply from DrLava. I should have the driver from Russia in a few days, it's currently in New York. Right now i don't have the funds to try out the diver from Australasia, if he made a single channel driver i would have went that route but at this time i only need one
What's the marking on the devices? I have access to some pretty comprehensive lists of SMD codes which haven't failed me yet!
The device that is connected to the gate is marked H1W the other is L2M, a six pin part 04M5, the last part is just an op amp that i found a data sheet to.
Thanks