MightyOhm Geiger Counter User Manual

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MightyOhm Geiger Counter Kit Assembly Instructions
(Updated 2019-08-01)
To build this kit, you should know how to solder. And it will be much easier if you have made other kits before.
But even if this is your first kit, do not despair! Just take your time and you'll be ok.
If you have never soldered before, Andie Nordgren, Mitch Altman, and I made a fun comic book that will teach
you how. You can find it online, translated into many languages, here: http://mightyohm.com/soldercomic
Ok! Let's get started.
1. First, check to make sure you have all of the parts.
You should have all of the components shown in the Bill of Materials on page 7. I suggest emptying the parts
from the ESD bag onto your work surface (don’t lose any!) or into a small box or bowl. Then, check each one off
the list as you sort through them.
Important note: If you purchased a case along with your Geiger counter kit (or it came as part of a bundle),
you'll want to open up the small bag of hardware that came with the case and look for a push-button with a long
(17mm) shaft. The long shaft lets you press the button after the case is installed on your kit. Solder the long
push-button last, after all of the other components. You can set aside the push-button that came with the
Geiger counter kit (the one with the short shaft), as you won't be needing it!
2. Solder the resistors.
First, take a look at the Assembly Diagram on the last page. This handy drawing shows you which resistors go
where on the circuit board. All components are mounted on the top side of the PCB.
I recommend soldering one at a time unless you know what you are doing!
The resistors can go in either way – polarity doesn't matter.
Bend the leads of each resistor straight down and push them through the holes in the board, then bend them out at
a 45-degree angle to keep the resistor from falling out.
Turn the board over, and solder each lead. Then, cut off the excess leads with your wire cutters.
In the steps that follow, you should trim all leads that stick out of the bottom of the PCB by more than 2 or 3mm.
3. Solder the diodes.
The orientation is very important, so make sure the stripe lines up with the black band shown on the board!
D1 is larger, and black with a white or silver stripe.
D2 is smaller, and reddish-orange colored, with a black stripe.
Both are labeled with the part number, although it can be hard to read.
4. Solder the slide switch (S1).
Make sure it sits flat on the board with the plastic lever sticking off the edge. I like to solder one of the leads, then
check if it’s flat. If not, I reflow the solder and push it flat with my finger. (Don't leave the soldering iron on the
lead too long, or you will burn your finger!)
Be sure to solder both of the small tabs on the ends as well as the three leads.

MightyOhm Geiger Counter Specifications

General

Brand	MightyOhm
Model	Geiger Counter
Category	Cash Counter
Language	English

Summary

Geiger Counter Kit Assembly Instructions

Check and Sort Parts

Verify all components against the Bill of Materials and sort them for assembly.

Solder Resistors

Mount and solder resistors onto the PCB, noting polarity is not important.

Solder Diodes

Solder diodes D1 and D2, paying close attention to their orientation and stripe markings.

Solder Slide Switch

Install the slide switch (S1), ensuring it sits flat and soldering all leads securely.

Solder Capacitors and Variable Resistor

Solder capacitors C3, C4, C2 and the variable resistor VR1, ensuring proper placement.

Solder Transistors

Solder transistors Q1, Q2, and Q3, carefully observing their orientation and markings.

Install Optional Headers

Install headers J5, J6, and J7 for data logging or hacking purposes.

Solder IC Sockets, Inductor, and Piezo

Solder IC sockets, inductor L1, and piezo speaker LS1, noting orientation requirements.

Solder Electrolytic Capacitor

Solder the polarized electrolytic capacitor C5, ensuring correct orientation.

Solder Tube Holder Clips and LED

Solder the Geiger tube holder clips (J1, J2) and the LED, ensuring correct orientation.

Solder Battery Holder and Push-button

Solder the battery holder (B1) and push-button (S2), noting the push-button variant for case use.

Install Integrated Circuits and Geiger Tube

Install ICs into sockets and carefully insert the fragile Geiger tube, observing polarity.

Test the Geiger Counter

Test the assembled kit by powering it on and adjusting the VR1 potentiometer for clicks.

Usage Instructions

Basic Operation

Understand LED flashing and speaker clicks indicate radiation detection. Use the push-button to mute sound.

PULSE Connector Pinout

Details the pinout for the PULSE connector (J6) including VCC, output, and GND.

Data Logging Setup

Connect to a computer via serial port (J7) using a 3.3V TTL USB-serial converter.

Data Logging Modes and Format

Explains CSV data format, baud rate, and three logging modes: SLOW, FAST, and INST.

Geiger Counter Case Assembly

Case Parts Check and Standoff Installation

Verify case parts and install standoffs onto the PCB.

Install Cover Plates

Attach the bottom and top cover plates using screws and lock-washers, avoiding overtightening.

Cleaning the Case

Clean the case using a soft cloth; avoid harsh cleaners that can damage acrylic.

Troubleshooting

Initial Checks

Verify battery freshness, contact, and check for a high-pitched whine indicating HV supply.

Component and Solder Joint Inspection

Inspect component placement, orientation, solder joints, and check for shorts.

Voltage Measurement and Tube Test

Measure HV supply voltage and perform a test by shorting tube clips for clicks.

Seeking Further Help

Consult forums or contact support for unresolved issues.