Introduction: MEGA DPDT Switch - Tank Style

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DPDT "double pole - double throw"  switch can be used for reversing polarity.  All though this method may be a bit crude, it works great for changing the direction of a motor – analog style.  This could be used for Controlling motors for robots, animatronics and Halloween decorations to name just a few helpful ideas!  See the last Step for Pictures of the great robot battle, controlled from this very switch!

Now their have been great Instructables on this all ready such as this one, by Troy (Firgelli Automations) and his Instructable, HOW TO: Wire a DPDT rocker switch for reversing polarity found here:

But I don't think many have covered the idea of actually producing the switch itself, at least on such a scale.  The photos below will show you how.  Mine was used to control a large fighting robot I built for another Instructable found below.

I wanted Lil' Timmy to have a tank style feel to the controls, since it did have tank steering.  Controlling it from little radio shack style DPDT switches just wouldn't cut it.  I wanted these switches to have some heft to them, something I could slam hard when making turns.  So i searched the internet and aside from some industrial switches nothing came close.  The purchased ones were astronomical in price and even then didn't really have the heft I was looking for.  So when something doesn't exist, make it it exist.  Not that hard actually, with a few simple variations anyone can make it. 

Step 1: Parts and Tools

Here is a list of what I used, beside it are examples of what you could use to substitute items you may not have access too.

Parts I used
  • 4      3/4" x 4.5" bolts per switch
  • 4      3/8" x 2" bolts per switch
  • 4      3/8" nuts per switch
  • 4      3/8" washers
  • 12    3/4" nuts per switch
  • 24    3/4" washers per switch
  • 2       Small iron hinges - try to match them so they are the same width as the tabs below, preferable with 2 holes per hinge leaf
  • 2       Tabs of iron plate about 1" x 4" about 1/4" thick, per switch
  • 1       Piece of 1/4" plywood about 2" x 3", per switch
  • 1       Piece of plywood 3/8" thick and at least 8" x 5" per switch, of course if you want a series of switches, mine was a piece  8" x 10"
  • 1       length of 3/8" steel rod about 7-8" long per switch
  • 1       Handle, I used 2.5" x 3" barrel type bearings, you could use anything, bored out pool balls, shrunken voodoo head perhaps
  • 1       Small tube of 2 part 5 minute epoxy

Tools I used:

* Drill and assorted bits, for drilling steel and wood
* Saw, to cut the plywood
* Angle grinder with a zip-cut disc
* Hobby grade or better device to weld with. OPTIONAL as one could braze, or perhaps even solder with epoxy used to re-enforce it.
* Basic hand tools, especially a socket and ratchet to match your bolts, for quicker connections

Step 2: Assemble the Parts That Move

  1. Start first with your tabs, drill 2 holes that will be used to mount to the plywood as shown in the pictures
  2. Next either drill 2 holes to bolt onto one leaf of the hinge, or simply weld in place as I did.
  3. Prepare your rod and nob "sounds so wrong"  Grind down or flatten with a hammer the last 3 inches of one end of the rod on 2 parallel sides, this gives you a nice flat section to drill through and mount onto the plywood.  Drill 2 holes like in the pictures
  4. If you haven't all ready, cut your 1/4" plywood into ----X---- squares and sand smooth
  5. Attach the nob, I simply welded my bearing onto the end of the rod, but if you are using something like a pool ball, car gear shift nob, or shrunken voodoo head - drill it out about an inch, insert your rod and glue it in place with a dob of epoxy or gorilla glue. Allow to dry
  6. Put a fillet of epoxy down the middle of the plywood square and screw the flattened end of the rod onto the wood square in your pool of epoxy - allow to dry - this is where 5 minute epoxy shines as your not waiting for ever - all though 90 second epoxy is even better but seems hard to come by in my neck of the woods these days
  7. Now apply 2 small fillets of epoxy running parallel with the rod onto the wood square, press your hinge tabs into the glue and screw in place - ENSURE THE 2 TABS AND ROD ARE NOT TOUCHING - DO NOT CROSS THE STREAM!  The wood square is acting as an insulator and allows the rod/knob to move both sections of the switch at the same time without sharing an electrical path
  8. Get your panel ready - try to plan ahead on this if you can.  If its being mounted in a cabinet, stand or what have you, make it to size.  Also plan on how many of these switches you may want to use.  As mine was used for tank steering, I needed one monster switch per motor - so I used 2.  I added a third one to control my rocket  turret.

Step 3: Mark & Drill Some Holes

  1. Get your panel ready - try to plan ahead on this if you can.  If its being mounted in a cabinet, stand or what have you, make it to size.  Also plan on how many of these switches you may want to use.  As mine was used for tank steering, I needed one monster switch per motor - so I used 2.  I added a third one to control my rocket  turret.
  2. Lay your hinged section you just built on your plywood and temporarily screw in place.  Move the handle back and forth to give you an idea of how it will move, You will need 2 of the large bolt to come into contact with each metal tab as you move it back and forth.  Once you have an idea of where you need to place the large bolts, mark and drill holes to fit the bolts tightly.

Step 4: Bolt Together

  1. Unscrew the switch handle you screwed on and drill holes in the screw marks to fit the smaller bolts snugly
  2. Where you marked the holes for the larger 3/4 bolts, drill holes for a snug fit of the bolts
  3. Now re-install everything and bolt down tight, move the switch back and forth adjusting the large bolts so the tabs make contact on both bolts at the same time.  See the build diagram for details!

Step 5: Wire It Up

  1. The wires hook up by simply clamping the stripped wire between 2 of the nuts on the bottom of the switch, see the diagram for clarity.
  2. Check out the link below for how the wires hook up or refer to the build diagram.

Once again, never put voltage through this you couldn't handle if your were to touch the live wires to your skin!  I used this on a 24 volt DC system, hooking up to 110v AC like your house current would pretty much end your instructable making/following career, or your life for that matter.  I suppose one could go to the trouble of insulating the switch further in theory  to make it safer, as all ready the handle section is isolated by the current, but.... Be careful and be warned!

Step 6: Use It

Now go use your new switch(s)!  I mounted mine in a pedestal podium thingy, The competition opted to build his into a prtable wearable candy stripper thing, with neck straps and a waist belt.  Threw in a couple pictures of the battle that was being controlled from these very switches, and of course the last picture is of my wiring for the rockets going up in smoke!   The wires to these switches and the switches them selves were just fine.  The radio shack SPST swtich - MELTED!

Make It Stick Contest 2

Participated in the
Make It Stick Contest 2

4th Epilog Challenge

Participated in the
4th Epilog Challenge