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Laser Diode Driver

Connection

Closeup
Closeup

The parts arrived for my adjustable laser diode driver! Components here are an LM317K with heatsink, 100Ω 10-turn precision potentiometer, 15-turn counting dial & a 7-pin matching plug & socket.

Driver Schematic
Driver Schematic

Here is the schematic for the driver circuit. I have used a 7-pin socket for provisions for active cooling of bigger laser diodes. R1 sets the maximum current to the laser diode, while R2 is the power adjustment. This is all fed from the main 12v Ni-Cd pack built into the PSU. The LM317 is set up as a constant current source in this circuit.

Installed
Installed

Here the power adjust dial & the laser head connector have been installed in the front panel. Power is switched to the driver with the toggle switch to the right of the connector.

Regulator
Regulator

The LM317 installed on the rear panel of the PSU with it’s heatsink.

Connection
Connection

Connections to the regulator, the output is fully isolated from the heatsink & rear panel.

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Portable Power Supply

Battery
Battery

This is detailing my portable multi-purpose power pack of my own design. Here is an overview, mainly showing the 4Ah 12v Ni-Cd battery pack.

Front Panel Right
Front Panel Right

Panel Features – Bottom: Car cigar lighter socket, main power keyswitch. Top: LED toggle switch, provision for upcoming laser project, Red main Power LED, 7A circuit breaker.

Front Panel Left
Front Panel Left

Top: Toggle switch serving post terminals, USB Port.
Post terminals supply unregulated 12v for external gadgets. USB port is standard 5v regulated for charging phones, PDAs etc.
Bottom: Pair of XLR connectors for external LED lights. Switches on their right control power & the knob controls brightness.

Additions are being made to this all the time, the latest being a 2W laser diode driver. Update to come soon!

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Chicom “500W” ATX PSU

Cover Removed
Cover Removed

Here is a cheapo 500W rated ATX PSU that has totally borked itself, probably due to the unit NOT actually being capable of 500W. All 3 of the switching transistors were shorted, causing the ensuing carnage:

AC Input
AC Input

Here is the AC input to the PCB. Note the vapourised element inside the input fuse on the left. There is no PFC/filtering built into this supply, being as cheap as it is links have been installed in place of the RFI chokes.

Input Side
Input Side

Main filter capacitors & bridge rectifier diodes. PCB shows signs of excessive heating.

Filter Caps Removed
Filter Caps Removed

Filter capacitors have been removed from the PCB here, showing some cooked components. Resistor & diode next to the heatsink are the in the biasing network for the main switching transistors.

Heatsinks Removed
Heatsinks Removed

Heatsink has been removed, note the remaining pin from one of the switching transistors still attached to the PCB & not the transistor 🙂

Transformers
Transformers

Output side of the PSU, with heatsink removed. Main transformer on  the right, transformers centre & left are the 5vSB  transformer & feedback transformer.

Output Side
Output Side

Output side of the unit, filter capacitors, choke & rectifier diodes are visible here attached to their heatsink.

Comparator
Comparator

Comparator IC that deals with regulation of the outputs & overvoltage protection.