Hobby Projects - Insulation tester, LED Circuits, Meters.

Thursday, October 17, 2013

LM317 based Regulated Power Supply

This is a Regulated Power Supply based on the LM317 IC. It will need a Boost Power Transistor and heatsink for higher currents. It is a versatile building block for stable instrumentation supplies. Consumer Electronic gadgets can use a SMPS chip. In case you wish to use a SMPS for a Precision Instrumentation Block, then take extreme care on Shielding and EMI-RFI.

LM317 based Regulated Power Supply

This is a General Purpose Chip, Series Regulation. It can be varied or trimmed. There is an Internal temperature compensated reference. The minimum trim value is around 1.2. In case you want a Low value voltage like 0.5 with a good current, then use a good negative supply to offset the 1.2 V.

The transformer can be s Split Bobbin with Pri-Sec copper shield foil.  This can be earthed along with the metal enclosure. C4 sends any hi-freq components to earth.  It is better if you do not earth the ground but use such capacitors. A Supply should simulate a a battery with both ends floating wrt Earth. A option to eartth the ground is fine. This also helps the user to configure his own dual supplies.

Q1 and R5 form a Short Circuit OR current fold back OR constant current mechanism. TP1 can be used to vary the output voltage.  Better use something like a Bourns 10T trimpot. An open preset may introduce a noise due to dust and vibration. I don’t remember why i added a zener DZ1, a diode may suffice.

See more at my Power Supplies Section.

Wednesday, October 09, 2013

Battery Monitor for your Boat or Car

This is a colorful, useful and educative project from Erlich Industrial Development, Corp. You will learn using Op-Amps as comparators and also LED bar graph analog display.

Battery Monitor for your Boat or Car

Voltage Monitoring is an Electronics board that allows you to connect 5 to 14VDC on one side of the board and get it corresponding LEDs light on the other side. Every Car, tractor or boat should have one.

Battery Monitor for your Boat or Car

The boards will allow you to easily monitor your 12V battery while powering from the same battery. The Terminal Block TB connector is included and makes it easy to use.

delabs notes

The LM324 is the Heart or Intelligence in this Circuit. There is a voltage divider and zener too. They have a kit and pcb to buy and build .

Important

A battery of a car can drive enormous amount of current, anything that is High-Voltage, High-Current or High-Frequency or a combination of these; are known to be high energy circuits. So as a precaution when you wire the positive to the car battery use an automobile fuse with holder like the one used outside the stereo player. The fuse has to be outside!

You could also use a fusible resistor in a metal box and keep it outside, the 12V positive has to go thru this. Any car/boat project needs this. A short circuit on PCB or Wire will blow fuse and everybody is safe.

Got it ..

Practical Electronics

Practical Electronics
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