diode laser driver

Hi, does anyone have a violet diode laser driver scheme, with a power control by monitor photodiode.

scalor7 said:

Hi, does anyone have a violet diode laser driver scheme, with a power control by monitor photodiode.

Click to expand...

the phr diodes dont have a monitor diode inside the diode casing

it's only need a costant current regulator like a lm317 or similar.
because i have two laser diode one have 3 pin and one have 4 pin .

If you got your diodes out of a phr sled then the 3-pin is the blu-ray and the 4-pin is the ir/red combo.

This post is really helpful:
[laser pointers dot com]/forums/YaBB.pl?num=1185701612

There is a nice image about half way down that I cant post here because of the no links for underposted members.

I used:
22mf Capacitor
1N4001 Diode
25 ohm pot
LM317 Regulator

All of which I got at Radio Shack (I hate their prices and selection, but sometimes I get impatient).

Here is a Resistance-Current graph using this setup and a phr blu-ray diode:

Best fit:
452.5x^-0.809

Some Points:

Resistance (ohms) - Current (mA)
08.3 - 85.
09.5 - 66.
015. - 51.
023. - 36.
036. - 26.
099. - 10.
124. - 09.

I ended up using two 15ohm resistors in parallel to get a base of 7.5, with the added minimum from the pot I ended up with that reading of 8.3ohms. So far I am quite happy with the power and utility from that range.

I hope this is helpful.

I'm building a little improved version of kernelpanic's mosfet + opamp driver (LINK), suits well for 803t sleds. It's a very low dropout design, thanks to the mosfet you can run this without any problem starting from 6.5V.



The schematic looks big, you can build this easily on a 4x4cm / 1.5x1.5 inch piece of breadboard without any problem. Powering it off a double cell lithium pack (7.2-8V) doesn't require any heatsinking for the mosfet. Assuming a 5V forward voltage for the diode, and the worst possible 8.4V charged cells, at 130mA you would loose in heat on the fet: (8.4V-5V-0.26V)*0.13A = 0.4W, nothing to worry about.

As setted, this driver allows an output variable between 0 and about 130mA.

Note: this driver is suitable for 803T sleds ONLY, since they are not case-grounded. If you are going to run ANY other negative or positive-case diode you must keep it insulated from the board/supply negative. connecting a case grounded diode sharing your supply ground with its case would short the entire mosfet - resistor group and blow up instantly your diode upon power-up.

Very nice. I like! I even have a spare diode to try it. I had always meant to switch the Vref to a zener. Been too busy playing with vacuum tubes lately...

+1 4 U for sure. ;D

Cheers,
kernelpanic

thanks very much, and for the diode with 4 pins ?

The four pin one is a low power red and ir combo.

To use it look at the circuit board that is attached to it. Two pins look to be connected, those are the ground. One of the other ones is for the red.

Then connect it to the driver, after setting it for the desired current (I don't know what they are capable of, iirc about 5mw). Only use four of the diodes on your dummy load.

I am going to make some adjustments to the actual circuit values, R1 first may be bigger, since we don't need any big current to feed the comparator. R1, if we're going to start off a 2-pack lithium supply, can be something about 3300ohm to limit at about 1mA the Vref sourcing abilities. If you are going to use the zener reference for more than one opamp-mosfet regulator, I think it would be a good thing to place in parallel with the zener a 10µF capacitor, to ensure some reference voltage stability.

Output current, as now, is chosen by the following formula:

((R3/(R2+R3)) * VDZ1 ) -> voltage at the comparator

since 0.3V accross the 2ohm resistor is equal to a current of I*R = 0.15A*2Ohm, we're expecting a ratio of 1mA/2mV.

so, our output current, will be:


((R3/(R2+R3)) * VDZ1 ) * 0.001A/0.002V

assuming R3 = 4700ohm, R2 = 56000 ohm, VDZ1 = 3,3V, our maximum current will be:

((R3/(R2+R3)) * VDZ1 ) * 0.001A/0.002V =
((4700/(4700+56000)) * 3,3V) * 1/2 =
0,077 * 3,3V * 1/2 = 0.127A. = 127mA

assuming a fixed 3v3 zener, we can simplify our formula getting it to:
((R3/(R2+R3)) * 1.65.

TTL modulation should be easy to acquire for this circuit, just add a BC548 or similar transistor with its junction parallel with DZ1. when you put a high logic level accross the small transistor, assuming a saturation voltage of about 0.25V (assuming it will switch far less than 10mA), we would get on the imput of our comparator a voltage of 19.2mV, equal to an output of 9,6mA. pretty enough to make our diode stop lasing.

Updated schematic with ttl blanking:



any comment about? I'm a bit worried about self oscillation inserted by the ttl system... maybe lowering C1 to get a more square comparator imput...

I've drawn a circuit board for this little driver... I've got, using smd components, a nice 2x2.6cm board. if anyone wants I'll put a pdf version ready to print.



edit: here's the pdf (A4 size) ready to print two 16x10cm boards with 20 drivers on each.

normal version: http://filebeam.com/2e8b139272f350c6da1b831b02cbee8c

"mirror" version: http://filebeam.com/23e0a430c2198bfd764b1bef2111958e

Nice Driver  
Just finished another driver for myself and i got it pretty
small too, just a lm317t circuit with adjustable pot
Roughly 0.78 inches in length and 0.74 inches in width

The ruler is in centimeters
2cm=0.78 inches

the LM317 is nice, but not that low dropout... if we're driving our sleds off 2 Li-ion cells it may get in troubles with medium charged cells at about 7V imput on the other side, the lm317 is far easier to use with other diodes since is a positive-rail regulator and doesn't need any damn insulated emitter

This is born most as a compact module driver, in the next days I'll try to build one and check for TTL mod too that would be the best

Good idea, yer i dont particularly like the dropout but its a good circuit to hav for labbies or just to test diodes out with nice fresh batteries :

Dropout drivers aren't the best we can choose, but, as for pricing, nearly all the times they are way cheaper to build than any other switching supply.

Most of the cases, the entire build as a LDO driver, like this mosfet one, costs about half than a boost driver, mantaining an acceptable overall efficiency. A LDO driving a blu ray (5.5V) off a 7V supply would have an efficiency near 80%, while its cost is far less than the expensive dcdc supply which, if we're lucky, runs at the same efficiency of a well-used ldo circuitry.

Switching are nice, really compact and useful, but if you want to build something cheap and don't wanna put 20$ on your driver, they aren't the best solution to choose. actually, building a regulator based on the schematic I've posted above, costs me about 5€, including the pcb and the etching process. If you are willing to spend, and get the smallest thing available, dcdc's are good. If you want to stay on the cheap side with still a good quality, ldo are imho pretty nice there

andrea87 said:

Dropout drivers aren't the best we can choose, but, as for pricing, nearly all the times they are way cheaper to build than any other switching supply.

Most of the cases, the entire build as a LDO driver, like this mosfet one, costs about half than a boost driver, mantaining an acceptable overall efficiency. A LDO driving a blu ray (5.5V) off a 7V supply would have an efficiency near 80%, while its cost is far less than the expensive dcdc supply which, if we're lucky, runs at the same efficiency of a well-used ldo circuitry.

Switching are nice, really compact and useful, but if you want to build something cheap and don't wanna put 20$ on your driver, they aren't the best solution to choose. actually, building a regulator based on the schematic I've posted above, costs me about 5€, including the pcb and the etching process. If you are willing to spend, and get the smallest thing available, dcdc's are good. If you want to stay on the cheap side with still a good quality, ldo are imho pretty nice there

Click to expand...

I agree.

The driver I posted was from the first laser I built. I was unhappy with the dropout of the LM317. I knew I could do better with a mosfet and an op-amp. (BTW it's still running strong at 135mA after 100+ hours )

But I don't think a home-made boost driver would be much larger or more expensive. In fact one could use the same op-amp/mosfet type setup to do a basic buck/boost PWM. Inductors are cheap.

Just a thought. :-?

Cheers,
kernelpanic

have you a datasheet of a phr-803T violet diode ?