Introduction: Mini Digital Geiger Counter
I decided to build a Geiger counter for my next project.
For the design, I wanted the device to mimic the CDV-700 series of counters from the 50s.
I looked for a kit that has similar CDV-700 configuration with functionality and accuracy that would also make it a good working device, after some searching I found one here from RH electronics:
For it to work it will require a Geiger Muller tube, one of these:
I printed this project on my home ABS printer with .15 mm resolution, the 3D files are attached for anyone to print themselves.
Just as a warning, this is a high voltage electronic project, meant for experienced electronic builders only. Be careful when handling this device.
- 3mm diameter 12mm long machine screws (hardware store)
- 1 bag of 1.5mm diameter 5mm long (M1.5 5mm screws) self tapping screws
- 2 aluminum rod 3mm (1/8") diameter
- 1 limit switch (electronic store / Amazon)
- 3 large tactile push buttons
- 1 lithium battery
Optional paint job:
- Decal paper clear and white (hobby store)
- White spray primer (hardware store)
- Yellow spray paint (hardware store)
- Gloss clear coat spray paint (hardware store)
To smooth out ABS/PLA print texture I use a bit of spray can primer, I recommend Krylon their primer is very good but hard to find I get them on Amazon. I tend to avoid any Rust-Oleum products due to extremely slow drying time, I have experienced gummy paint even after a week of drying, bad for sanding.
For large simple parts, you can also alternatively try XTC-3D 3D Print Coating, but be careful applying it, too much will cover intricate details and may change the dimensions for interlocking parts:
Step 1: Assemble Geiger Counter Kit
Follow the provided instructions and build the electronic kit.
Solder 4" length wires for the power switch, LED, and control switches, these need to be extended for relocation.
Geiger tube clips will also need to be extended, solder larger gauge wires to these leads, 2" length (final configuration will be as shown in the 3rd image).
Connect the battery and a power switch
Test run the kit make sure it works.
Be careful, the tube runs on high voltage electricity read and obey all warnings in the instructions.
To test the kit you need a source of radiation, after some research I found these old lantern socks on Ebay, I think It was manufactured in the 70s it contains a bit of thorium which emits radiation that is detectable by a Geiger counter.
Its not dangerous to have one, but I keep mine in a metal box just in case...
Step 2: Assemble the 3D Printed Components
Sand all the bonding edges and press the components together, laying and clamping the components flat on a table helps with edge alignment.
The parts can be attached with glue, but I prefer bonding them with solvents.
For ABS plastic brush on acetone, for PLA plastic MEK substitute on the part line to bond parts together. (image1-2)
For the top surface start by assembling the 3 buttons and use 1.5mm screw on the retainer. Attach the button tops, align the buttons through the holes before permanently bonding them to the top plate. (image 3-5)
Bond the board holder in place, as seen on the last picture. (image 6-7)
Attach and bond the 2 screw mounts (image 8)
Lastly bond the battery bracket together (image 9),
Align the battery bracket with the switch bracket and bond all the legs (image 10)
Notice that the screws should be accessible through the battery bracket holes (last image)
Step 3: Build 2 Latches
Brush solvents on all the 3D printed parts, this will help strengthen the parts, when the solvents are dry assembly can start.
Bend the aluminum rod into a rectangle around some nails, measurements in the image are the distances between the nails.
Bend the aluminum rectangle (image 2-4). Adjust this bend if the latch is too tight or loose.
Snap all the components together and use the 1.5mm screw to attach to the bottom case.
Step 4: Finishing and Painting the Printed Case (optional)
I only finish the outside face of the case as the inside is usually not seen.
Start by sanding the bottom case against a flat surface, this will ensure a smooth flat surface.
Then use a sanding block and sand the flat parts of the upper surface and hand sand the detail sections.
Apply spray primer, at least 5 coats making sure it dried between coats.
Then after the primer dries completely wet sand the surface. Sanding and priming process can be repeated until you are happy with the result, after several coats the 3d printed surface texture should disappear.
Apply a final coat of primer and spray paint the case yellow.
Print and apply the water slide decals, I use decal fluid to enhance adhesion.
Wait for everything to completely dry and coat everything with the spray clear gloss.
For more details on painting and decal application see my micro arcade cabinet tutorial.
Step 5: Assemble the Top Section
Drill out the limit switch mounting holes with 3mm or 1/8" bit (image1-2)
Insert the limit switch as shown in image3 secure with 1.5mm screw on the printed pin or glue.
Attach the rotary power knob, hold the knob from the other side and attach the clicker (image3) screw the knob components together with 1.5mm screw, make sure the clicker is positioned in the proper notches and it closes the limit switch when the knob is twisted to the right (image3-6) bend the metal switch lever if it does not make proper contact.
Take note of which leads on the switch need to be connected to the board later, If the knob is stuck or hard to twist loosen the screw a little.
This knob is the main power switch be familiar with its function for safety and troubleshooting.
Assemble the 3 selection buttons and secure them with a 1.5mm screw.
Insert the LED to the LED bracket (image 7)
Drill out the led hole making sure the LED fits through (Image 8)
Screw the bracket with 1.5mm screw. (image 9)
Step 6: Insert the Geiger Kit
Final assembled configuration is shown in (image 2-4) I also wrote the polarity for the Geiger tube on the bottom of the PCB to prevent wrong connection. Please be very careful on these final steps.
Attach the metal spacer pin to the LCD board with the provided screw and insert the LCD board make sure it is secured to the pins visible in (image 1)
Connect all the wires from the main board to designated buttons, LED, and the limit switch.
Taking care with the wires, insert the main board under the battery bracket make sure the back is slotted properly.
Connect main board to the screen, screw to the metal spacer pin and secure the main board with 3mm screws, make sure the tube holder is attached on the left screw (image 1-4) keep the loose wires clear of the limit switch so that it does not hinder its operation.
Attach the battery through the bracket (image 2-4)
Attach the Geiger detector tube and connect it to the provided clips (image 2-4)
Make sure the power knob is OFF before proceeding and the limit switch lever is clear of wires and other obstructions.
Carefully plug the power connector to the main board with tweezers.
Close and latch the case before twisting the knob to activate, this kit produces high voltage to run the Geiger tube.
Obviously, do not open the case while the device is running.
To use, hold the handle and hover the device over samples
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