Build a 120 vac to 18vdc Power Supply for DC Tool

[EdwardNorton]

Hello, I have an older 18vdc / 20 amp cordless circular saw that my charger has been misplaced which really doesn't matter because the batteries went bad. I am wanting to build an 120vac to 18vdc power supply that I can directly connect to the the saw. My plan is to build a mini bench top / hobby table saw out of the tool.

Anyone here feeling generous with their time & knowledge concerning how I would go about doing this?

Regards,
Edward Norton

 

[Alec_t]

Welcome to EP.
It will be cheaper, simpler and quicker to buy an off-the-shelf switch-mode power supply than to build one.

 

[davenn]

Anyone here feeling generous with their time & knowledge concerning how I would go about doing this?

Welcome to EP.
It will be cheaper, simpler and quicker to buy an off-the-shelf switch-mode power supply than to build one.

Hi Edward
I agree with Alec
an 18V 20A PSU is a serious project and unless you are VERY SKILLED in electronics
don't even contemplate building one

 

[brevor]

I agree, but I don't think even an "off the shelf" switch mode PSU would handle the startup current of that motor. My suggestion would be buy a new saw.

 

[AnalogKid]

A 360 W linear power supply probably is what you were thinking about when you asked. It would need a 500 W power transformer. Think 5 pounds of iron and copper, larger than a softball. After that it is big diodes and big capacitors. The circuit is relatively simple, but the scale of the components is an excellent lesson in why the switching power supply was invented.

ak

 

[EdwardNorton]

I really wanted to use this saw for a bench top table saw for cutting small parts rather than risking my fingers going it on my commercial table saw but we don't always get what we want right? OK guys, I appreciate the input very much!

 

[EdwardNorton]

I just looked up a 360 W linear power supply & damn was I shocked in the prices, $350 to $1,200! I have to agree with Sheldon Cooper in that it would be cheaper to buy a new saw. Found this one for $150... Thanks again!

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