Pyrography Machine homemade

The Pen 

Ben Aragon

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The bowl again 

Ben Aragon

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Re: The bowl again

bill dotten

>good to know those plans work. I wish that I had them before I paid for my store-bought machine

Great design work

Bill

Re: Pyrography Machine homemade

jeff jilg

>Very nice Ben - both the woodturning and the homemade implementation of the woodburning unit. I have questions in 3 areas.

Where did you get supplies from? Specifically the phenalic tube?

Also why does an extra circuit need to be added? Wouldn't it be possible to directly connect the pen connections to +5v and COM (gnd), or even +3.3V and COM? (If it requires the circuit I probably won't make it since I'm not sure what a MOSFET is.)

The wires passing thru your phenalic tube don't look insulated. I guess since they are stiff and glued into the tube they shouldn't short. Is this correct?

thanks in advance,

Jeff

A couple of questions

John Trant (Baltimore/WashDC)

>Where did you get your MOSFET? I built the same device some time ago but it failed due to the improper MOSFET. Radioshack does not sell one with the required parameters. The heat sink of my MOSFET got much hotter than my pen.

What gauge NiChrome wire are you using for your pen tip?

John

Re: Pyrography Machine homemade

Ben Aragon

>Jeff,

I got the phenolic tube from fishcarver.com http://www.fishcarver.com/online_specials.htm you can get the NiChrome wire from him too. I used 16 gauge NiChrome wire, I think 18 gauge would be better. The pen and cord wire needs to be one gauge thicker than the NiChrome wire. My cord wire is 14 gauge and it is to thick and stiff for my liking.

The extra circuit is to control the temperature of the tip of the pen, basically it�s a switch to turn on and off the current to the pen. If you connect the pen to the PS directly it would get cherry red, way to hot to use. The MOSFET is just a switch and the one I used can handle about 60 amps. The other part of circuit produces an adjustable square wave that tells the MOSFET when to open and close.

The NiChrome wire has to be silver soldered to the pen wire. The tip gets so hot regular lead solder will melt and the tip will just fall out. I used 1/8� copper tubing to couple the NiChrome wire to the pen wire. There is no insulation on the pen wire because the heat from the torch when silver soldering melted it, so I stripped it off. The pen wire is solid 14-gauge wire and won�t touch, very stiff. I used RCA jacks to make the connections.

If you�re unfamiliar to electronics it might look intimidating but it is really not that difficult. If you�re a wood turner you can do this. The soldiering might take a little practice, everyone knows an electronics guy named Sparky ask for some help.

I got all my parts form Newark electronics, http://www.newarkinone.come/ . Here is a drawing I made up of how I did it with a list of parts.

Best Regards,

Ben

Re: A couple of questions

Ben Aragon

>John,

I got all my parts form Newark electronics, http://www.newarkinone.come/ .

The MOSFET I used was IRF3708 the NiChrome wire is 16 gauge and the pen and cord wire is 14 gauge.

Best Regards,

Ben

Re: Pyrography Machine homemade

jeff jilg

>Hello Ben - thank you for the detailed responses to my questions. You have cleared up all the questions I have asked and I appreciate it. Although I have done a lot of computer programming, I have no circuit training.

It looks like the outside of the PS has the following:

- a green lamp (light)

- a switch just below the lamp

- 2 outlets for 2 pens on the right side.

The switch is wired from the COM and PS-ON pins from the diagram - correct? Is the rest of the external PS unmodified or did I miss something? How do you adjust the pot?

You have 2 common wires to the +5v and also the COM. Is that to help with the load so the wires don't heat up?

Your diagram helps a lot - I can see that the timer chip and the MOSFET switch basically regulate power to the nichrome wire. Did you mount the MOSFET to the powersupply heatsink? The other homemade unit had an additional large heatsink on it.

Curiosity questions:

The 5 ohm resistor across the COM and +5V is confusing to me since it doesn't hook into the circuit at all. What the heck does that resistor do?

Similar question - what does the 12 ohm resistor between +12v and COM do?

One thing I like about this project is that it is really inexpensive and it will allow me to re-use an old PS which just happens to be sitting around :-)

Thanks again for the answers to-date.

Re: Pyrography Machine homemade

Fred in NC

>"The 5 ohm resistor across the COM and +5V is confusing to me since it doesn't hook into the circuit at all. What the heck does that resistor do? "

Without this resistor, the whole thing will not work! It is a "feature" of the dual voltage power supply, which was designed to work with computer motherboards.

When the capacitors fully charge, if there is no current drain in the 5V side, the supply will shut down. The resistor fools the power supply into thinking it is connected to a motherboard. Some people use a light bulb instead; anything that uses enough of the 5V voltage will do.

Questions and Answers

Ben Aragon

>Jeff,

Here you go, all connection are done through the Power Supply 20 pin connector that goes to mother board.

Question 1:

It looks like the outside of the PS has the following:

Answer 1:

Correct about the:

- a green lamp (light) connected to the 12V line as an indicator.

- a switch just below the lamp to turn on the PS, try to get a PS that has an ON/OFF switch already

- 2 outlets for 2 pens on the right side. RCA plugs and a selector switch

Question 2:

The switch is wired from the COM and PS-ON pins from the diagram - correct?

Answer 2:

You only have to install the switch between COM and PS-ON pins if the PS doesn�t have an ON/OFF switch already.

Question 3:

Is the rest of the external PS unmodified or did I miss something? How do you adjust the pot?

Answer 3:

The rest of the PS is unmodified, the pot has a full turn knob on it, pots are adjustable. You can buy 1, 5, or 10 turn pots.

Question 4:

You have 2 common wires to the +5v and also the COM. Is that to help with the load so the wires don't heat up?

Answer 4:

Good eye you don�t miss much. Yes double up on the common and the 5V line to the pen to handle the current load.

Question 5:

Did you mount the MOSFET to the powersupply heatsink?

Answer 5:

I mounted mine to the PS heat sink near the fan, if you can�t buy a heat sink.

Question 6:

The 5 ohm resistor across the COM and +5V is confusing to me since it doesn't hook into the circuit at all. What the heck does that resistor do? what does the 12 ohm resistor between +12v and COM do?

Answer 6:

Thanks for the help Fred. Fred is right the PS needs to see a load on the 5V and 12V lines to turn on.

Recycle that old PS and have fun with it I know I did.

Best Wishes,

Ben

Re: Questions and Answers

jeff jilg

>Thank you very much Ben and Fred. I appreciate the detailed responses, and I'm going to copy this thread to a file in my woodturning folder as a reference. Heck, I think I even learned a little bit about circuitry so this was a good exchange for me!

I'm currently distracted from woodturning because I'm rebuilding my pool deck. But this woodburning project will be next up on the list. Thanks again guys for taking the mystery out of the electronics! This has been a great thread, and it will save me ~$110 on a woodburning unit! Plus it looks like a fun project to build!

Thanks!

Jeff

Re: Pyrography Machine homemade

Pascal Oudet

>Ben, verry happy to hear you built your own version and it works.

and it's even better that you are able to provide a good "customer service" and answer the technical questions for me ;-)

I will update the page with your link to your electronic components supplier. I was quite disappointed that RadioShack didn't carry the right component, and was frustrated not being able to suggest a good supplier.

happy burning,

Pascal