O-like, Green module driver dummie test?

[jander6442]

I'm going to post a question here also. Those drivers that use the cathoide or (case positive) such as the o-like blue ray driver. How in the world do you rig your dummie load for a current setting. The same would be for a typical green driver.

I can get, of course the current setting with the rig already built, but how can you get the dummie rig set up for a pre built unit. :beer:

 

[HIMNL9]

Uhm, not sure what exactly you are asking , so ..... green modules uses IR laser diodes, and they have usually 1,8 to 2,2 V of VF, so, 3 diodes must be enough for simulate them ..... and, if your module don't have the positive connection on the back (mean, the only way for power up it is using the module body as positive), just attach the +V to the positive output of the load .....

The ones from o-like have not common positive, if i recall correctly ..... they just work as any other standard modules, so the dummy load .....

 

[jander6442]

so if you attach the +V on the test load and the - on the driver your saying omit the + on the driver altogether? I think I have tried this.

The o-like blue ray driver has the +Vout as the loop in the circut. I must be missing something. What would be the steps involved in dummie testing for current on an o-like cause its not like the domestic drivers we have here. Anyone?

 

[BShanahan14rulz]

Jander, you are trying to measure the output of the green driver? You will need to remove the laser diode from the circuit if you do not know the precise electrical characteristics of that particular diode. From there, you would rig up 3 diodes and your current sense resistor in place of the laser diode.

If you leave the laser diode in place, some of the current goes through the laser and some of it will go through your test load. The ratio depends on how the equivalent resistances of the two loads compares.

 

[jander6442]

^ I have that. What I'm asking is setting the current on a o-like driver you cannot
just hook up the batt. to the driver then hook up your dummie load + - then test your current over the 1 ohm diode mV = mA. A typical rckstr dummie load is what I'm using.

the typical way of doing this is to hook up the Vin+ Vin- then Vout+ to the dummie
load Vout- to the dummie load. Power up the unit and measure using DVM set in current across the 1 ohm resister to get the measurement of mV= mA.

 

[HIMNL9]

same for the o-like modules ..... only, remember to connect FIRST the dummy load to the driver, and THEN to power up the module.

 

[jander6442]

^ then how about the ir drivers or ones with case positives they ARE different.

 

[HIMNL9]

Uhm, maybe is my bad English, but i don't see the point, sorry.

Positive case driver is different just cause is a current sikn drive (and as any current sink drives, the common power line from the LD to the power supply is the positive one, NOT the negative one) ..... mean, opposite to "normal" LM317-types, that have the GND that go straight from the GND input to the cathode of the LD and the regulator that work on the positive branch, in current sink drives, the positive go straight from the +V input to the anode of the LD, and the regulation of the current works on the negative branch, usually with a mosfet (and the sense resistor) between the cathode of the LD and the GND (and is for this reason that they can use the case as positive, with green module, that having IR LDs inside, are anode-to-case connected)

Like in this driver, as example:

But, for regulate them with a dummy load, there's no special things to do ..... if the module have the +V and GND pins, just connect the dummy load and power the driver from them, if instead you have one of the modules that have only the spring contact for the GND, and takes the +V only from the body of the diode, then connect the dummy load in place of the diode, connect the positive of the output to the +V, the spring to the GND (don't forgot to bypass the switch, if there's one), and do the reading on the resistor, in the same identical way of the other drivers (the only difference can be the lower VF of the IR diodes, so for emulate an IR diode with the dummy load, is enough to use 3 diodes)

 

[jander6442]

Ok HIML I'm closer to understanding I just dont get this statement...

"then connect the dummy load in place of the diode, connect the positive of the output to the +V, the spring to the GND (don't forgot to bypass the switch, if there's one), and do the reading on the resistor, in the same identical way of the other drivers".

Thank you for your patience and understanding.

 

[HIMNL9]

Ok, as you know, driver boards have, usually, 2 points for power supply, and 2 points for connect the LD ..... some drivers for green modules, (cause they take the +V from the body of the diode) only have the spring for the GND (minus of the battery), and no other pins .....

If you have a driver board that have all the 4 pads, use it as any normal driver ..... solder the dummy load, with the correct polarity, in place of the LD, then power up the driver and measure the voltage on the resistor .....

If you instead have a green laser driver that have only the spring contact, and not the positive one ..... in this cases, you must first take away the IR diode (if present), or look where the diode must be soldered and individuate the case (+) and pin (-) pads ..... at this point, connect the negative of the battery (or PSU) to the spring, bypass the button, if present (you may keep it pushed with something, or solder a wire across it), connect the dummy load with the correct polarity, connect a wire for the +V to the positive of the dummy load (or on the pad where the case pin of the diode must be soldered, it's the same), then power up the driver and measure the voltage on the resistor. THIS FOR GREEN LASER DRIVERS ONLY.

Sometimes, can be found very old drivers that was deriving the feedback from the photodiode built in the IR LD, but these drivers are very old, and it's difficult to find them, actually ..... these ones are the only ones that can give some problems, cause they need the IR LD connected, for work properly ..... but i think it's difficult to find them, actually.

By the way, the o-like for blue LDs drivers, uses the case positive just for convenience, as far as i know, but they have a very bad design, and are NOT the same thing as an IR/green driver, these ones are switching drivers, where the IR/green ones are current sink drivers ..... if you use these ones:

then you must connect the dummy load, with the correct polarity, from the "laser diode +" and the "laser diode -" pads, and the wire for the +V from the battery to the "VCC +" pad (where can be connected the case of the LD, if insulated from the LD chip), and NOT connect the +V of the LD to the VCC+ ..... yes, they have designed the driver very bad, in matter of pads dispositions and connections .....

 

[jander6442]

@ HIMNL9 Thank you sir, for your time and effort if ever I could repay you for that just ask. jander6442