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Workbench Power supply 0-30Volt 0-3A

This is my first fully homemade device i ever built and i built it before having enough knowledges on electronics. I found the circuit on the internet here. It is a very stable power supply with current limiting 0-30V adjustable and 0-3A adjustable which is enough for most of the electronic circuits. I also made a modification and added an Operational Amplifier for inverting the output Voltage in order to have symmetric voltages for powering Op Amps. The only disadvantage is that the negative voltage is 1 Voltage less than the positive (eg. if you have  a +6V positive output then the negative output will be -5V) and starts working after +1V of positive voltage.

The front panel is a printed cardboard.

PSU 0-30V 0-3A

PSU 0-30V 0-3A

Here you see the backside with the 2N3055 screwed on a heat sink

PSU 0-30V 0-3A

PSU 0-30V 0-3A

PSU 0-30V 0-3A

PSU 0-30V 0-3A

PC PSU to WorkBench PSU

Most of digital circuits needs a fixed stable voltage for powering ICs like a microcontroller. So a very good solution for these voltages can be a computer power supply which gives you the fixed voltages of +/-12V +/-5V and +3.5V. By the option of symmetric voltages you can also supply operational amplifiers. Here you can see a modification i made to a PC PSU putting it into a metal/aluminium box making it look more professional and safe.

The front panel is a printed cardboard.

PC PSU

 

PC PSU

The cooler hole was cut by my Jigsaw Base

PC PSU

 

PC PSU

 

Inside

Testing the MC34063 PSU for filament supply.

Today i started testing the MC34063 PSU i have just designed, supplying the six VFD-Tube filaments together at the same time.

Testing MC34063 PSU

MC34063A Step-Down Converter 12V to 1.2V 750mA

The IV-12/11 vfd tubes need 1.2Volt for the filament about 100mA each. In my clock project i'm going to use 6 tubes so the total draw current will be about 600mA which is to much for a linear regulator like LM317. The LM317 can be used, but it will be need a big heat sink to keep it cool. So i designed a step-down converter based on MC34063A, a pulsed regulator, which is also power efficient.

I could have been used a resistor in series with the filament but if any tube filament get burned then the other 5 will draw more current and get burned too. Also i could have been used the AVR to regulate this voltage than using the MC34063A but there wasn't more free space on the chip.

MC34063A Step Down Converter design.

The design is based on the MC34063A's datasheet. In this design i regulate the voltage to 2.5Volt because the tubes want to have a negative voltage about -1volt to get fully powered off. So i have put two diodes in series (with ones kathode connecting to others anode) connecting the negative filament pin to GND. By this, each diode works as a supply voltage providing 0.6V x 2 = 1.2Volt.   2.4V-1.2V =  1.2Volt which is the supply voltage needed for powering the filament.

 

Protoboard testing

MC34063A ProtoBoard