80-100mW Green China laser
A while ago I posted about my green dpss laser from china. I've seen someone else mention these lasers before, but I cannot find the post. Anyway, I decided to post this information to anyone who wants to use it.
The laser module looks like this:
The driver is a 5v smps with two power transistors on the top pcb (closest to the heastink) and driver circuitry and adjustment pots on the bottom pcb. The diode driver uses one of the power transistors and is a low side driver. The tec controller appears to be a linear one, but I don't know for sure. On the top pcb there are also two pads through which one can tap the 5v supply to supply other parts eg. secondary driver for red.
The bottom pcb contains all the smart electronics. The driver is TTL and following the circuit it appears to be controlled by the left pot (the pots facing upwards with the adjustment screws facing you) as there is a direct link from this pot to the driver through the white wire integrating the controller to the board. The right pot appears to be the temp adjustment. I haven't tested these claims exactly as I do not want to mess up the factory default for temp.
The head:
The head has an external tec and fan to regulate the internal temp of the LD and crystals. Disassembled, the setup contains only one tec to cool the LD, and crystals which are glued together into a single assembly.
The head is connected to the driver with an 8 pin connector (don't know the type).
Pinout is the following;
Grey: Fan -ve (Tied to -ve at PCB)
Green: Thermistor -ve (Tied to -ve at PCB)
Yellow: TEC -ve
Brown: Thermistor +ve
Black: LD -ve
White: TEC +ve (Tied to +ve at PCB)
Red: LD +ve (Tied to +ve at PCB)
Blu: Fan +ve (Tied to +ve at PCB)
To convert the module to analog, I just pulled out the red and black wire, and connected them to an external driver. Driver was still left on so as to allow proper functioning of the tec cooling.
I have had some time on my hands and tried to map out the laser diode driver. Disassembled the driver completely, and I've managed to map out the major power components for the LD and peltier and also the driver circuitry for the laser diode driver.
Diagram is self explanatory. The large resistors I believe are shunts. During operation, the voltage measured across the 2 ohm shunt was measured to be 1047mV i.e 1.047V. By ohm's law this should give a current of about; I=V/R: 1.047/2= 0.524A or 524mA. This is the factory set current for my module. When the TTL pins are shorted for blanking, the voltage therefore the current measured was zero, thus no threshold current is present.
When the circuit was followed through to the control circuitry PCB following the path was difficult. If one looks back up to the image showing the driver circuitry, the laser diode current and modulation control are regulated by the IC on the side of the connector (the one joining the top and bottom PCBs) and the other IC on the raised pcb module - which is connected by the wires. I wish to be able to modify the module without the need of an external driver i.e. hijack the power components of the driver with an extra board which can be glued in and wired like the raised PCB. From some Examination of the path, the raised pcb was added later and it 'affects' the other ic on the board regarding the LD driver i.e. a hot fix which converts the module to the chinese style TTL. Will look further into the matter, as this would allow an analog conversion to be much easier (just a small SMD pcb - not to difficult to make and solder on a homemade level). The blue wire appears to be acting as a source or is supplied by a voltage of 2.5V, hence the '25' marking on the PCB.
Analog fix Done - Testing on the way.
Conversion INFO:
Conversion needs to be done on both the large board and a secondary board (either my homemade version or the heavily modified added on chinese TTL board). On the large board, modifications mainly include changing the already present potentiometer regulating the current to the LD to have a lower output voltage - this now assumes the function of the threshold pot. The other mods include removing the old wires - save the black, red and yellow ones, and a resistor and a capacitor. The last mod includes the usage of the unused op-amp on the lower op-amp IC to attenuate the threshold voltage level.
Instead of R36 two wires are to be soldered: yellow and cyan in diagrams - make sure these do not come together across the pads.
The second includes the production of a second op amp circuit. This was either through modding the old TTL board or by creating a new one. All SMD parts were scavanged from the old TTL board itself, and old Motherboards and for the new homemade board, a variable resistor from a DVD-Drive laser head assembly - there are supposed to be 2 - just be gentle when desoldering them. If you go with the homemade board option, try to find as thin as a copper clad as possible - else do as I did and sand its thickness down. The old TTL board can be easily removed and the new one glued instead of it. Also make sure the lm358 is soldered in the correct orientation.
Homemade board:
Here is the circuit diagram:
If anyone needs the Eagle files please send me a PM..
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Originally Posted by LaNeK779
And besides, it was a bit rewarding at the end to know all the innards of this little greenie.
Mine has been under construction due to fund limitation for a year now, slowly buying parts and such. If you have access to a milling machine you could try to build your own version mounts, check round for all the types currently available for sale and others built by members. Still need to buy dichros, finish blue and check out the options for red.
