Dimmer Control

 The Thrifty Rocketeer blog continues...

I have commented before about how sometimes one hobby will overlap with another, and some of the tools from one will be used for another.

Well, this is another one of those times.

Recently, our Amateur Radio club held a group build during the warmer weather, outdoors on a picnic table at the county Red Cross chapter house.  This basically means that we borrowed their parking lot, worked at their picnic table, and used an extension cord to borrow a cup of electricity to power a soldering pencil or electric drill.

I won't bore you with the details of what we were building or how many people were involved, except that it was a pleasant fall afternoon and we were done within a couple of hours, so that others could attend or watch the college football game.

But one thing we asked club members to do, was purchase the supplies from the group leader, and to bring a few tools with them.  In most cases, the newer club members didn't have a soldering pencil, but went to their nearby ACE Hardware or Lowes store and bought one new off the rack. As it turns out, enough of us brought our own, and so there was always a hot soldering iron/pencil available for the few electrical connections that needed to be soldered.

But this also triggered in me the memory of my first soldering iron/pencil, and how I pressed a wood burning tool into service for years and years.  I have shared some of that earlier.

And it occurred to me that some of the newbies, might not know the proper temperature range for an iron.  In my case, for years, I simply unplugged and reconnected the power cord to my wood burning tool to regulate the temp.

A couple of decades later, when my wife got interested in stained glass, she needed a stronger iron that could put out more watts and really heat up the lead and solder for her work. My little soldering wood burner wasn't enough, and so she bought a soldering iron along with all of her supplies at the glass shop.

She frequently would complain that the iron was getting too hot, and that she wished she could tone it down a bit.  This comment coupled with my discovery of my old Heathkit lamp dimmer control produced an idea for us.

I brought out my controller and wired a very short cord adapter so that her 3 prong grounded plug could be powered off the two element NON-polarized plug in the side of the dimmer control. It worked fine...just a little 4 inch extension cord that allowed her to use the lamp dimmer to control the temperature of her massive soldering iron.

Well, jumping to modern day, I remembered this innovation and offered to the newbies an opportunity to build a dimmer control unit to help control the temperature of their soldering pencil. 

I wound up thinking about this and wandering through the Habitat for Humanities ReStore looking for ideas and parts.  As it turns out, I found just about everything that I needed, but the prices really surprised me!

I was able to find a short lamp power cord with two element plug, an electrical outlet cover plate for both power socket and a flip switch, a used wall dimmer control, screws for the cover plate, power plug, wire nuts and electrical tape.  The one thing that I couldn't find was a plastic two-gang electrical junction box, which I found at Lowes for just $4...the most expensive part in the whole kit.

All I did was construct a simple basic circuit:  I threaded the lamp cord in through a strain relief clamp in the junction box and joined the hot side of the wire to the dimmer control lead with a small wire nut.  The other side of the dimmer control lead went to the brass screw hot side of the power outlet socket. The silver terminal side attached to the common side of the lamp cord to complete the circuit.  Both the power outlet and the dimmer control were screwed down into the junction box (just as if it were mounted in a dry wall) and the cover plate was then screwed down on top of those two controls. Now it was all contained and safe.

In this way, the voltage in the power outlet sockets was being controlled by the dimmer control knob, which went on and off with a push, and rotated to dim the power.  Anything... lamp or soldering iron... plugged into the sockets is controlled by the dimmer knob.

I offered the kit to the newbies, but not a single one took me up on it, probably because they haven't had a lot of need for the soldering iron yet, but also because their pencil may not grow too hot.  Remember, it was my WOOD BURNING TOOL that was overheating.

Since constructing this for under $7, I have thought of a few revisions:  

    1) to add a couple of non-skid rubber foot pads onto the bottom-side of the junction box so that the box won't skid on the table top. 

    2) to change out the two-element power socket with a 3-prong grounded socket, to accept 3 prong plugs. (This would require grounding the socket and the supply power cord also.)  

    3) to snip the brass connector between the two brass terminal screws, making each of the two power sockets independent of each other.  This would require an additional wire from the wire nut to supply power to the newly freed brass terminal screw, supplying it with un-dimmed current.

This last innovation would keep the dimmer control in line with one power socket while keeping the other straight wired.  The advantage would be to plug a high intensity desk lamp (or maybe a small exhaust fan) into the straight power socket to aid visibility at table top, while keeping the temperature control on the other socket.  Perhaps they should both be labeled at that point.

As rocketry sometime requires soldering a few components together or replacing some launch clips, etc,  I offer this simple circuit as a way to control a  powerful soldering iron and limit the heat and extend the life of the heating element. (I understand they are designed to burn out and fail in a shorter period of service nowadays.)

This has been the Thrifty Rocketeer saying, save your power and extend your heating element by building this simple dimmer controlled power supply.