Geiger Lamp - Now With Illuminated Dial




About: I'm cheap and like to use what I have on hand and I really enjoy taking things apart to salvage parts. Rather than be a precise engineering type of person, I'm more of an enthusiastic tinkerer. Making things...

This Instructable will document how I converted an old civil defense Geiger counter (O.K. technically it's an ion chamber, but most folks haven't heard of those so we'll just call it a Geiger counter) into a lamp. Why do this you may ask? I work in a field which touches on radiation and we just moved to a new work space that isn't quite as well illuminated, so I decided to make a radiation themed lamp. I had seen this done before, but didn't like the way the conversion was done. That version had the meter horizontal so you couldn't see it very well and used a pull chain socket. My version has the meter vertical and I use the original instrument knob to turn the light on and off. Plus the guy who made them was charging an exorbitant amount of money for them. I figured instead of paying for something I really didn't like I would make my own for less than $20.

I haven't added a shade at this point, but that will hopefully be rectified soon. I think I'll try and find one that is yellow and black or yellow and magenta as these are the official color schemes for radiation postings in the U.S. I've also considered making a stained glass shade in these colors, but that will have to wait for warmer weather. Whichever option I go with will play on the radiation theme.

The green twist is that this project uses almost all reused materials. I only bought a new socket, nuts to hold on the feet, and a new rotary switch.

Step 1: Materials

These are the materials I used to make my Geiger Lamp:

  • 1 survey meter ( I used a CDV-715)
  • A cord with a plug
  • White wire
  • Black Wire
  • A rotary switch (On/off not reostat)
  • Wire nuts
  • Electrical tape
  • Feet (4)
  • Nuts (4)
  • Lock nuts (4)
  • Tubing with lock washers and nuts
  • Lamp socket
  • Hot glue

The meter was acquired from a friend that works for an agency that was disposing of non-functional meters. You may also be able to pick one up at a surplus store, an auction or through a catalog. I bought a lamp at the thrift store to get the lamp tubing I needed.

Optional materials for LED illumination of the dial:
  • LED
  • Wires
  • Batteries (3 volts in total)
  • Scrap metal (I used a penny)
  • Plastic container (I used a pill bottle)
  • 2 rubber bands (Not pictured)
  • A rotary switch (On/off not reostat)

Step 2: Tools

I used the following tools for this project:

  • Drill press
  • Hand Drill
  • Drill bits
  • Drill bit sizer
  • Dremel (with grinding bit)
  • Clamps
  • Wire cutters/strippers
  • Pliers
  • Wrenches
  • Metal punch
  • Ballpean hammer
  • Deburring tool
  • Bench Vise
  • Hot glue gun

Step 3: Disassembly

The first thing we need to do is take apart the meter and remove the guts. Fortunately most survey meters are easy to open so the user can change the batteries. They are held shut with a latch on each end. Simply undo the latches and then lift the top off the case. If you want to keep the internal workings intact lift carefully. Some models have components attached to the face plate and the bottom of the case that are connected to each other by wires. If you open the meter enthusiastically you'll rip out the connecting wires.

Once your meter is open begin taking out the screws that hold the components in place. Save parts such as the screws and battery holder for future projects. Pitch the rest in the garbage or recycling bin as appropriate. Leave the display in place so it still looks like a meter.

Now lets talk knobs. You may have pulled out all the screws inside the meter and the components are still in place. More than likely they are being held on by the control knobs. Knobs on scientific equipment are typically held on by one or two set screws. In newer equipment these are hex head screws. (My meter is so old that it used flat head set screws.) Use either a screw driver or allen wrench to remove the set screws so you can take off the knobs. WIth the knobs removed the guts should fall free from the face plate.

Once the knobs are off be sure not to lose them or the set screws as we will need them for the project. I threaded the screws back into the knobs and put them aside for safe keeping.

With the knobs safely stowed away, I next removed the original rotary switch so I can replace it with a new switch. I did this because this meter ran on a 1.5 volt battery. Trying to use a switch made for 1.5 volts to control a 110 volt lamp struck me as a bad idea, so the old switch has to go.

In order to drill out a hole for the new switch I needed to take the handle off the meter. It was secured in place by a single screw with a lock washer. Like the knobs you may want to thread the screw back into the handle to keep track of it. Once the handle is removed we are ready to drill.

Step 4: Drilling the Face Plate

We need to enlarge the hole that the old switch passed through in the face plate in order to accommodate the new switch.

First remove the screw-on casing and nut that is intended to hold the switch in place. Then use a drill bit sizer to determine the diameter of the switch.

When you have this information load the appropriately sized bit into your drill press (or hand drill). Then clamp down the face plate and drill out the hole the original switch passed through.

If you're adding the LED illumination of the dial repeat this process for the zero dial in the lower left hand corner.

Step 5: Drilling the Case

We now need to drill a total of six holes in the lower case of the meter. Four holes for feet, one for the cord and one for the tube which will hold the socket.

The first hole in the case will be for the power cord. You can measure and mark the exact position you want or just eyeball it. I just eyeballed it and made a mark. Since I wasn't widening an existing hole, I used a metal punch to make a small dent in the case. This will keep the bit from walking.

Next I determined the diameter of the hole I would need by feeding the cord through various holes in my drill bit sizer. I chose a diameter that was a little bigger than the cord so it wouldn't get damaged when passing into the case.

With that done I put the appropriately sized bit in the drill press, clamped down the case and drilled the hole.

Next I marked out the location of the feet on one end of the case with the eyeball method described above. With that done I clamped it into my bench vise (using my work protectors to keep the finish from getting marred) so I could drill it with my hand drill. With the case held securely in place I used the metal punch to dent each foot mark. I sized the threaded posts on the feet and loaded the correct bit into my hand drill. And then I drilled out the holes for the feet.

When the foot holes were done I flipped the case around and made the hole for the lamp tube via the same process.

Step 6: Hole Clean-up

Once the holes are drilled you will probably need to clean off some ragged edges. For the relatively smooth holes I used a hand deburring tool to remove any little sharp things I couldn't see. For the larger pieces I used my Dremel with a grinding bit and pliers to remove the sharp pieces. This was followed by a quick treatment with the deburring tool.

Additionally the hole for the lamp tube was still a little small, so I used the Dremel and grinding bit to enlarge the hole.

Step 7: Assembly

Now that the case penetrations have been completed we can start to put the lamp together.

I began by attaching the feet. I threaded a regular nut onto the post of the foot. Next I inserted the post into one of the holes I drilled for the the feet and secured it in place with a lock nut. Make sure you have enough clearance beneath the meter so the latch doesn't scratch the table the meter will sit on. You may have to make some adjustments so the lamp sits levelly.

With the feet in place I moved on to the lamp neck. I threaded one nut and a lock washer onto the the lamp neck. Then I inserted the end into the case and placed another lock washer and a nut onto the lamp neck. I then tightened both sides with a wrench.

With the lower portion of the case completed I turned my attention to the face plate. I removed the retaining nut from the switch. I placed the switch so it protruded from the front of the face plate and secured it with the nut. I tightened it up with a pair of pliers. I then attached the knob to the switch using the set screws we saved when disassembling the meter.

Step 8: Wiring

Now that the structure of the lamp is complete we need to wire it.

The first step is to cut two pieces of wire about 12 inches long that will run from the socket down into the lamp (I used white and black) and to strip the ends. WIth that done attach these pieces of wire to the socket. The neutral wire (white in my case) is secured under the silver colored screw on the socket. The hot wire (black in my case) is secured under the brass screw.

Once the wires are attached to the socket screw the socket base onto the top of the lamp neck and pass the wires through the lamp neck and into the meter casing. With that completed snap the socket cover into place.

Now strip the ends of your power cord and feed it through the hole in the back of the meter. Twist the white neutral wire and the neutral wire in the power cord together with a wire nut. (In your typical two wire cord you can tell the wires apart by their texture. The neutral wire will have insulation with a rough texture and the hot wire will be smooth.) With the neutral wire completed twist together the hot wire from the power cord and one of the switch wires with a wire nut. Then twist together the other switch wire and the socket hot wire. You should now have a complete circuit. Plug in the lamp, turn the switch and see what happens. (If you want a bit of cheesy drama say "LET THERE BE LIGHT!!!" in your most deity like voice).

The last part of the wiring is to make sure it stays put. I accomplished this with copious amounts of hot glue. I put a few inches of slack in the power cord and then clamped it to the case. With that done I squeezed hot glue around the cord where it entered the back of the meter. When that glue cooled I glued the slack to the bottom of the case as well.

With that done I reconnected the handle to the face plate and hot glued the disconnected zero knob to the lower left corner. In the future I may hook a second switch to this knob and use it to have a blue LED light up the instrument dial. A buddy of mine suggested building a rectifier circuit that would have the needle on the instrument display move when the light was turned on. I need to refine my electronics knowledge and skill a little bit before trying this though.

Step 9: LED Dial Illumination

I mentioned this the possibility of doing this in step eight when I first published this Ible and I have finally attempted it. For those of you looking to power the LED off the 110 plug this step won't help you. I powered my LED off of two AAA batteries as my electronics skills aren't that advanced.

First I removed the zero knob in the lower left hand corner of the face plate. Then I drilled out the original hole to accept the new switch (see step 4). WIth that done I put the new switch in place and while the diameter of the hole was correct the depth wasn't. It turns out the face plate is thicker around the zero knob hole so it won't be possible to secure the new switch with a nut. To solve this I hot glued the switch to the back side of the face plate. Once the glue cooled I secured the knob to the new switch with set screws and made sure it would turn properly.

With the switch in place I turned my attention to the LED. My meter had a foam block just below the the dial that was orginally used as a spacer for the ion chamber. I cut a slot into this foam to secure the board that holds the LED. With the LED in this slot I glued it in place with more hot glue.

I wired together the negative leg of the LED and one of the switch wires. I then crimped electrical connecters to the other switch wire and the wire linked to the positive leg of the LED.

Now to power the LED. I used two AAA batteries taped side by side. I rigged up a battery holder by hot gluing a penny to the bottom of a plastic pill bottle that held the batteries snuggly. I cut the excess off the pill the bottle with my Dremel so the tops of the batteries would be exposed. (REMOVE THE BATTERIES PRIOR TO TRIMMING THE PILL BOTTLE). WIth batteries re-installed I matched up the polarity of the wires to the batteries and used the rubber bands to hold the wires in place. (It took a little experimentation with wrapping the rubber bands to keep them from slipping off the batteries, but it appears to be working great now.) I wrapped the exposed portions of the wire with electrical tape.

Now my meter dial will have a spooky blue glow whenever the mood strikes me.



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    74 Discussions


    9 years ago on Step 9

    This is such a cool idea, I'm dying to try it! One question, though: How heavy is the empty case? Specifically, is it bottom-heavy enough not to topple over at the slightest provocation once you put a shade on the thing? Also, I'm wondering about that shade. What sort of thing could I cobble together that would suit the project? Maybe something with the CD emblem printed on it? A "Duck and Cover" instructional poster from the '50's? Anybody else have any ideas?

    3 replies

    Reply 3 years ago on Introduction

    Well,I finally got around to making this bad boy. (I didn't illuminate the dial, but maybe someday.) Problem (and this is the one I anticipated six years ago): The gutless case is too light, making the thing top-heavy. Others may have had success as-is, but mine falls over. I have made a steel base plate and sprayed it with yellow Krylon (a pretty good match for the original CD yellow), but I'm still working out the details of attachment. While I work on this, did anyone try anything different?


    Reply 3 years ago on Introduction

    I haven't had tipping issues myself but I had to really adjust the feet to get it level. I would try putting some weight in the form of scrap metal inside the case. Once it's heavy enough to stabilize the lamp I'd epoxy it to the case so it doesn't shift and tear the wiring loose when you move the lamp. A sandbag inside might work also but that could introduce dust into the works.


    Reply 9 years ago on Step 9

    It's not all that heavy but once I got the legs level it is very stable. I've adjusted the shade with nary a wobble in sight.


    7 years ago on Introduction

    Hi I made one of these lamps and i have lit the dial with and LED and made the needle move to around the 3.5r area and powered it all off the mains.

    This is what I did to do it.

    I wired in the lamp as per normal for 240v (im in the UK) but i used a 1megaohm rotary switch to turn it on and off using the original range knob.

    I also ran off the 240v side a 240v - 12v transformer that i robbed out of an old aquarium pump or something. i opened the unit up and soldered the 240v main feed onto the input side of the transformer. this gave me 12v out the other side.

    off of this 12v supply i now wired in a 560k resistor (i think - its covered by heat shrink now) followed by an LED - this illuminated the dial.

    Also off of this 12v side I wired in a variable trimpot , sorry i just experimented and found one that worked out of my box of bits) that dropped the voltage and meant i could adjust the needle to fall where i wanted. i just set it to around 3.5r/hr.

    to power the meter i simply wired positive up to the +ve side and negative to the -ve side. 12v was to much and pegged it out right off the dial so hence i used a pot.

    By doing all this i can switch the lamp on with the original range switch, which turns on the bulb, lights up the LED dial and moves the needle up the scale.

    With hindsight i would prob use a few LEDs as the dial isnt that bright, but other than that im happy.

    Here is a really crud wiring diagram to explain it, dont flame me as i have no electronics background i just fiddle and made this diagram purely to illustrate this point. If its wrong or i have badly mucked up please tell me!!

    i have labelled it as i wasnt sure of all the symbols....

    see attached, and also this photo on flickr which illustrates the dial

    1 reply

    8 years ago on Introduction

    Just a quick note: If you're meter comes in the original civil defense cardboard box, be very careful of the staples that reinforce the corners. They are razor sharp. I have an inch long cut being held shut with three sutures to prove it.


    9 years ago on Step 9

    quick question: i have everything i need for this EXCEPT the actual geiger counter/survey meter. where can i find this model of survey meter to either purchase/get from donation?

    1 reply

    Reply 9 years ago on Step 9

    Several folks were able to find them on E-Bay. There are also several places that sell surplus Civil Defense Meters. Try Googling "Civil Defense Meter" or CDV-715 and you may find some that way.


    9 years ago on Introduction

    Sweet! I didn't know you added the LED lights. Awesome. Now you just need to put it on a timer so it can act as a night light for you when you're wandering through your house in the middle of the night.


    9 years ago on Introduction

    Can you post a pic of the full schematic that was in the box?

    if anyone is interested I have a quantity of these meters available for purchase. im in minneapolis, but will ship for the cost of postage

    7 replies

    Reply 9 years ago on Introduction

    That may depend if the US government has any restrictions on exporting such instruments. I wouldn't have a clue if there is or not, if there is Australia may be an exemption. In any event sending a gutted cabinet may get around any restrictions that exists. I suppose someone up to no good would send it one piece at a time. Like J. Cash's caddy. :)

    I would be very interested. I plan to use a modified LED flickering "Tea candle" to provide both the light and some meter movement. Have thought about adding a speaker for a little ticking as well. Might as well go for it! Please let me know how much & how to pay. Thanks.


    Reply 9 years ago on Introduction

    If you figure out how to get the meter to move and have a small ticking sound could you let me know?


    Reply 9 years ago on Introduction

    If you have any more, I'd be interested too. Moving into a new home and need to make some cool furniture for it :)