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Last December, I discovered a 12V 30A power supply and 12VDC 30A dimmer controller on Amazon and wondered if they might be suitable for constructing a wood burning controller capable of hotter tip temperatures. (Yes, I saw the YouTube Battery Charger videos.) Here's what I came up with:

At first, I tried connecting the burning pen directly to the dimmer outputs, but the tip got very hot when the dimmer was turned only part way up. I resolved this by adding a 0.5ohm 400W resistor (four 2 ohm 100w resistors in parallel + heatsink) in series with the burning pen to act as a voltage divider. This provided proper heating to the burner tip. The downside is that the resistors get VERY HOT (700 degrees when turned full ON) and must be mounted on a heatsink to dissipate that heat. Not very elegant, but it works. I intend to add a shield around the heatsink to prevent touching the resistors/heatsink accidently.

The essential parts were a 12VDC 30A switching power supply, a 12VDC 30A PWM dimmer controller and four 2 ohm 100W resistors The cost for these items on Amazon was $50. The case, switches and other misc. connectors cost $50 from Jameco.com. I do not recommend trying to build this if you are not familiar with basic electricity and proper soldering techniques.. If anyone would like more details, please contact me directly.

Jim,

I was intrigued by your idea and started my own investigation into power supplies for woodburners. I have a Colwood Detailer, which has a 37W power supply. I have found this unit to be good for detail work but not powerful enough for larger tips. The unit you describe above started with a 360W power supply (12V x 30A = 360W). I am not at all surprised that you found this to be excessive for most tips. The dimmer control on your unit did not apparently allow for fine enough adjustments at the low end of its power range.

I have not yet done so, but am tempted to purchase a unit such as below:

This unit allows for variable voltage and current, thus by first turning down the current, the variable voltage control should allow for dexterous adjustment of power without the need for external, hot resistors... I will post again in the event that I follow up on my own proposal.

Thank you,

Mark

Mark,

Looks good! I saw the listing for this power supply on Amazon and it has a multi-turn pot for adjusting voltage, allowing fine control. At 300W max output, our application would be a conservative use of this supply. I checked my unit tonight when it was adjusted for a proper burn, and the voltage drop across the glowing nichrome pen tip (0.3 ohms) was1.48 volts resulting in a current flow of 5.28 amps or 7.8 watts of power.

The only potential problem I see would be the danger of accidently adjusting the voltage too high, as the burning tip requires only 1 to 4 volts to light up, depending on tip resistance..

FYI, I would recommend using 16 or 18 gauge nichrome wire for the tips. The tips I've made from 20 gauge wire were somewhat flimsy and bent easily when subjected to pressure.

Nichrome Resistance

16 gauge = 0.25 ohms / foot

18 gauge = 0.41 ohms / foot

20 gauge = 0.64 ohms / foot

Let me know if you do order this supply. Might be worth the gamble.

Jim