# NEW IR PINBALL TESTERS: PART ONE

**Source:** Pinball News Website  
**Type:** article  
**Published:** 2022-10-16  
**Beat:** Pinball

**URL:** https://www.pinballnews.com/site/2022/10/16/new-ir-pinball-testers-part-one

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## Analysis

Pinball News publishes a comprehensive hardware guide for building DIY infrared (IR) transmitter/receiver tester boards using modern ATtiny85 microcontroller clone boards. Todd Andersen of Pinball Renaissance updates his 2006 design to eliminate soldering requirements, reduce costs, and use readily available components. The article details component specifications, wiring diagrams, and assembly instructions for home hobbyists to diagnose IR opto-switch failures in pinball machines.

### Key Claims

- [HIGH] Infrared transmitters and receivers have been vital components in electronic pinball machines since 1987 — _Opening statement establishes historical context for IR component use in pinball_
- [HIGH] Todd Andersen originally wrote about building IR testers in 2006 in an article on Pinball News — _Article explicitly references the 2006 Pinball Renaissance article by Todd Andersen_
- [HIGH] EDATtiny boards from ElectroDragon had a 20% failure rate, though the manufacturer refunded for failed units — _Todd Andersen directly states this from his personal experience sourcing boards_
- [MEDIUM] Modern computer compatibility with Arduino devices became problematic after 2015 — _Todd Andersen lists this as a reason for updating the design, but does not elaborate on specifics_
- [MEDIUM] Global chip shortage caused ATtiny85 microcontroller prices to quadruple and availability to dwindle — _Todd Andersen attributes component pricing and stock issues to the chip shortage, but notes he is 'assuming' based on supply chain patterns_
- [HIGH] Complete ATtiny85-based clone boards became cheaper than standalone ATtiny85 microcontroller chips — _Todd Andersen directly compares pricing and discovered complete boards cost less than individual chips_
- [HIGH] The ATtiny85 can handle 40.0 mA of current per input/output pin, which is sufficient for IR tester applications — _Technical specification extracted from ATtiny85 datasheet and cited in article_
- [HIGH] Pinball Renaissance sold out of discrete component-based IR Tester fob sets some time ago — _Todd Andersen states these sets 'sold out some time ago' and describes fulfilling a special request that led to the design update_

### Notable Quotes

> "However, useful as these components are, they have one characteristic which makes it difficult to troubleshoot them (or the circuit of which they form a part). The infrared light they either transmit or sense is usually invisible to the human eye."
> — **Pinball News article introduction**, Opening section
> _Establishes the core problem that DIY IR testers solve—invisible IR radiation makes diagnosis difficult without specialized equipment_

> "Many people can't solder. Many people don't want to solder. With this new version, connections can be simply wrapped and hot glued, or even bolted in place."
> — **Todd Andersen**, Reasons for design update section
> _Key accessibility improvement in the updated design; removes soldering barrier for hobbyists_

> "When I shopped reputable mainstream retailers to try to purchase enough boards to replenish stock, I discovered two things. First, assuming in large part due to the global chip shortage, prices had over quadrupled. Second, and again I'm assuming related to the assumed reason behind the first, boards were wildly out of stock."
> — **Todd Andersen**, Component sourcing challenges section
> _Documents the impact of global chip shortage on hobby electronics pricing and availability_

> "For the price I found for the standalone ATtiny85 chips, I could purchase two complete EDATtiny boards. This included the same shipping and handling costs."
> — **Todd Andersen**, Tiny Boards section
> _Demonstrates the extreme market inefficiency created by supply chain disruptions_

> "In addition to affordability, I noticed the use of holes and their spacing on these boards made connecting a few discrete electronic components quite easy. I realised this made these boards ideal for pinball hobbyists who may want to build their own IR Tester boards."
> — **Todd Andersen**, Tiny Boards section
> _Explains why EDATtiny boards were selected beyond just cost—form factor supports hobbyist assembly_

> "The ANODE goes to the +5 Volt source on your ATtiny board; not the +5V pin."
> — **Todd Andersen**, IR LED (Sender) specifications section
> _Critical polarity warning for component assembly; prevents common wiring mistakes_

> "Most Digispark clones will have their on-board LEDs connected to P1. If yours is not the case, use 0 (for P0) in the #define you will add to the 'Blink' sketch featured in Part Two of this article."
> — **Todd Andersen**, Digispark Clone Model Identification section
> _Documents variation in clone board manufacturing that affects software configuration_

### Entities

| Name | Type | Context |
|------|------|---------|
| Todd Andersen | person | Founder/operator of Pinball Renaissance in Minnesota; original 2006 IR tester designer; author of updated design published on Pinball News |
| Pinball Renaissance | organization | Minnesota-based pinball repair/hobbyist business run by Todd Andersen; previously sold discrete component-based IR Tester fob sets; now focuses on documentation and design updates |
| Pinball News | organization | Educational and reference website for pinball repair and hobbyist content; published original 2006 IR tester article and current hardware/software guide series |
| ElectroDragon | organization | Chinese electronics supplier; manufactures EDATtiny microcontroller clone boards used for updated IR tester design |
| EDATtiny | product | One-inch diameter ATtiny85 microcontroller-based development board manufactured by ElectroDragon; used as base platform for updated IR tester design; had 20% failure rate in Todd Andersen's order |
| Lilytiny | product | ATtiny85 microcontroller clone board; cosmetically different from EDATtiny but functionally identical; alternative to EDATtiny for IR tester construction |
| Digispark | product | Original square ATtiny85 development board from DigiStump; design foundation for EDATtiny and Lilytiny round clone boards; includes onboard LED and USB programming interface |
| DigiStump | organization | Electronics company that originated Digispark microcontroller board design; maintains official Digispark documentation and tutorials |
| ATtiny85 | product | 8-bit AVR microcontroller chip manufactured by Atmel; core processing component in Digispark and clone boards; supports 40mA per I/O pin; programmable via Arduino IDE |
| Arduino IDE | product | Open-source programming environment used to write and upload sketches to ATtiny85 and Digispark boards |
| QED123 | product | Industry part number for IR LED (infrared transmitter) with 880nm wavelength; used in IR sender tester board; equivalent to old Williams Pinball part A-16908 |
| QSD124 | product | Industry part number for IR transistor (infrared receiver) with 880nm sensitivity; used in IR receiver tester board; equivalent to old Williams Pinball part A-16909 |
| Williams Pinball | organization | Historical pinball manufacturer; legacy parts reference used in article to cross-reference modern component specifications (A-16908 IR LED, A-16909 IR transistor) |

### Topics

- **Primary:** IR (Infrared) Opto-Switch Technology and Diagnostics, DIY Microcontroller Project Design, ATtiny85 Microcontroller Boards and Clone Hardware, Pinball Machine Repair and Troubleshooting
- **Secondary:** Global Chip Shortage Impact on Hobby Electronics, Component Sourcing and Supply Chain Challenges, Electronics Assembly Methods (Soldering vs. Alternative)
- **Mentioned:** Open-Source Hardware and Arduino Ecosystem

### Sentiment

**Positive** (0.78) — Article is constructive and solution-focused. Todd Andersen presents design update as response to real hobbyist pain points (soldering barriers, component availability, cost). Tone is educational and encouraging. Mild acknowledgment of frustrations with supply chain issues, but overall message is that DIY alternatives provide viable path forward.

### Signals

- **[community_signal]** Pinball News continues commitment to technical education for home hobbyists through detailed hardware/software guides authored by industry practitioners (confidence: high) — Multi-part educational article series with detailed schematics, component sourcing, assembly instructions, and code resources demonstrates ongoing editorial investment in hobbyist community
- **[market_signal]** Global chip shortage created extreme supply chain inefficiencies: complete ATtiny85 boards cheaper than individual chips; prices quadrupled; mainstream retailers out of stock (confidence: high) — Todd Andersen documents discovering complete EDATtiny boards cost less than standalone ATtiny85 chips and encountering quadrupled prices and stock-outs when attempting to replenish inventory from mainstream retailers
- **[product_strategy]** Redesigned IR tester kit removes soldering requirement through use of wrapable/glueable connections, significantly lowering barrier to entry for hobbyists (confidence: high) — Todd Andersen identifies inability/unwillingness to solder as primary pain point and redesigns to support 'wrapped and hot glued, or even bolted in place' connections
- **[technology_signal]** Modern computers (post-2015) have compatibility issues with Arduino devices, necessitating design refresh to use newer microcontroller platforms (confidence: medium) — Todd Andersen cites 'Modern computers (post-2015) do always not play nicely with Arduino devices' as primary reason for update, but does not elaborate on specific incompatibilities
- **[technology_signal]** Update from discrete electronic component-based IR testers to microcontroller-based design reflects evolution in hobby electronics accessibility and cost structure (confidence: high) — Todd Andersen explicitly designed updated version to eliminate soldering requirement and leverage cheaper microcontroller boards rather than discrete components

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## Transcript

Infrared (IR) transmitters and receivers are vital components used in many electronic pinball machines since 1987. Commonly referred to as ‘opto-switches’ or simply ‘optos’, paired-up transmitters and receivers allow contactless sensing of movement in order to register a target hit, detection of a ball’s position or the sensing of movement by a mechanical device.

However, useful as these components are, they do have one characteristic which makes it difficult to troubleshoot them (or the circuit of which they form a part). The infrared light they either transmit or sense is usually invisible to the human eye.

That makes it tricky to tell whether an IR transmitter is radiating as intended, and whether an IR receiver is detecting IR radiation correctly.

Back in 2006, Todd Andersen of Pinball Renaissance in Minnesota wrote an article describing how to build your own matching IR transmitter and IR receiver to aid with testing. When the associated button is pressed, these car-fob-sized devices would either transmit a constant IR beam, or light an LED to indicate the detection of IR radiation, thus allowing you to diagnose faults with both IR transmitters and receivers.

While extremely useful and functional, much has changed in the world of electronics in the past sixteen years. The availability of the component parts has changed as has the cost, while newer methods have become easily afforded.

So, Todd has looked anew at the problem and devised an alternative, automated, more modern and more readily-available alternative you can build at home.

In this first article he looks at the hardware used in his design, how the components are chosen, and includes links to the components’ suppliers for more information, while the second part concentrates on the software needed, providing code you can use immediately or modify to your own requirements.

Over to Todd…

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Having previously put myself in your shoes, I’ll summarise two of my main reasons for deciding an earlier Pinball News article about building your own IR testers possibly needed an update…

1. First and foremost, soldering.
• Many people can’t solder.
• Many people don’t want to solder.
• With this new version, connections can be simply wrapped and hot glued, or even bolted in place.
2. Technology is changing.
• Modern computers (post-2015) do always not play nicely with Arduino devices.
• Microcontroller technology is now cheaper, smaller, more capable, and newer.
• Software (sketches) can be easily modified for use with various board/component combinations.

Pinball Renaissance sold a ‘fob’ version of the IR Tester sets – sender and receiver pairs – to pinball hobbyists. These testers were built using discrete electronic components and sold out some time ago.

While fulfilling a special request to make more, I noticed that I lacked enough discrete components to complete said order. At that point, I realised I could update the IR Pinball Testers from all-discrete electronic components, to use newer Arduino clone boards.

Most of the clone boards I had in stock were subsequently made into IR Pinball Testers. These new IR Testers are now sold out as well, with completion of this special request marking these new Arduino clone board based IR Tester sets as no longer available.

Using the Arduino clone boards to complete the special order significantly dwindled my stock of the specific microcontroller clone board I used.

When I shopped reputable mainstream retailers to try to purchase enough boards to replenish stock, I discovered two things. First, assuming in large part due to the global chip shortage, prices had over quadrupled. Second, and again I’m assuming related to the assumed reason behind the first, boards were wildly out of stock.

This forced me to search even harder. In doing so, I discover I could purchase complete Attiny85 microcontroller-based boards for less than the cost of the Attiny85 microcontroller chips alone.

So, I decided to purchase these new-to-me Attiny85 based clone boards.

Tiny Boards

To replenish my stock, I found the EDATtiny from ElectroDragon. These one inch diameter boards are designed to be ‘wearable’ and feature the ATtiny85 microprocessor, being programmable via the Arduino IDE software.

However, these Chinese clone boards had a 20% failure rate, although the manufacture did refund me for those failed boards.

Per the manufacturer, these red EDATtiny boards are, “Compatible with lilytiny, digispark bootloader, to upload sketch please add board digispark 16.5mhz in arduino IDE.”

![The top and bottom of the EDATtiny board](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/01-new-ir-testers.jpg)

The top and bottom of the EDATtiny board

As an alternative, the layout and board colours of the black and purple Lilytiny clone boards (shown below) are only cosmetic differences from the EDATtiny boards I used (shown above). These Lilytiny clone boards should otherwise be identical to the EDATtiny boards.

![The Lilytiny ATTiny85 boards](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/02-new-ir-testers.jpg)

The Lilytiny ATTiny85 boards

All three round boards are actually clones of Digispark square boards. In fact, and as introduced earlier, DigiStump started it all with their Digispark boards. After all, they are, “Home of the Digispark.”

For the price I found for the standalone ATtiny85 chips, I could purchase two complete EDATtiny boards. This included the same shipping and handling costs.

In addition to affordability, I noticed the use of holes and their spacing on these boards made connecting a few discrete electronic components quite easy. I realised this made these boards ideal for pinball hobbyists who may want to build their own IR Tester boards. And, the built-in/onboard LED of the EDATtiny saves us from having to bother with even more discrete electronic components.

For those who want to try this at home, the few supporting discrete electronic components needed can be easily attached without soldering. The legs of these components can be wrapped in place and secured with hot glue. Or, the legs can simply be bolted in place if you prefer.

Discrete Components

Here are the additional components you will need:

IR LED (Sender – 880nm wavelength)
Industry Part Number (PN): QED123
Substitute PNs: QED121, QED122, 276-143, 276-143C
Old WMS Pinball PN: A-16908
(Note: Some pinball parts sellers may sell this component already mounted on a board.)
New WMS Pinball PN: 5671-12731-00
(Note: This is usually sold as just the discrete component itself.)

!Williams Pinball Ir LED (Sender – 880 nm wavelength)

Williams Pinball IR LED (Sender – 880nm wavelength)

![IR Transmitter specifications](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/11-new-ir-testers.jpg)

IR Transmitter specifications

This diode has polarity. This means it can only operate correctly in circuit when placed in a specific orientation. The ANODE goes to the +5 Volt source on your ATtiny board; not the +5V pin.

A 940nm wavelength side-looking version of this photodiode (PN: QEE113) can also be procured. It should work in pinball machines and may be useful for getting into smaller spaces like the small slot in between opto-interrupters, as used on drop targets and flipper mechanisms. However, that photodiode has not been tested for use in this article.

IR Transistor (Receiver – 880nm sensitivity)
Industry PN: QSD124
Substitute PN: 276-145 or 276-145A
Old WMS Pinball PN: A-16909
(Note: Some pinball parts sellers may sell this component already mounted on a board.)
New WMS Pinball PN: 5163-12732-00
(This is usually sold as just the discrete component itself.)

![Williams Pinball IR Transistor (Receiver – 880nm sensitivity)](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/03-new-ir-testers.jpg)

Williams Pinball IR Transistor (Receiver – 880nm sensitivity)

![IR Receiver specifications](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/04-new-ir-testers.jpg)

IR Receiver specifications

This transistor also has polarity. That means it can only operate correctly in circuit when placed in a specific orientation. The COLLECTOR (non-flat side) goes to the +5V pin on your ATtiny board.

A side-looking version of this NPN phototransistor (PN: QSE113 or QSE114) can also be sourced. It may be useful for getting into smaller spaces like the small slot between opto-interrupters, as used on drop targets and flipper mechanisms. However, that phototransistor has not been tested for use in this article.

Resistor (10kΩ/10kOhms – 10,000 Ohms)
1/4 (0.25) Watt
Axial Leads

![A 10K Ohms resistor](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/05-new-ir-testers.jpg)

A 10k Ohms resistor

ATtiny85 Datasheet

Atmel 8-bit AVR Microcontroller with 2/4/8K Bytes In-System Programmable Flash
ATtiny25/V / ATtiny45/V / ATtiny85/V
Rev. 2586Q–AVR–08/2013
The ATtiny85 datasheet can be found, in its entirety, here.

I’ll save you from having to look through all 234 pages of the datasheet and show you a summary of the most important part we need to know about the ATtiny85 chip.

![A small section of the ATtiny85 Datasheet](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/07-new-ir-testers.jpg)

A small section of the ATtiny85 Datasheet

The ATtiny85 can handle 40.0 mA of current per Input/Output pin. This is plenty for our simple use.

Digispark Schematic

![The schematic for the Digispark design](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/08-new-ir-testers.jpg)

The schematic for the Digispark design

From the schematic above we can see that the Digispark (and most clone boards) have an onboard LED, as previously written about in this article. And, that a resistor (R5) is used to limit that LED’s current.

More general information on LEDs and more technical information, including limiting the operating current of LEDs, was covered in a previous Pinball News article.

Taking an excerpt from the second, more technical article:

| |
| --- |
| The following formula is based on Ohm’s Law. Rdrop = (Vin – Vled) / Iled |

When reviewing manufacturer’s specification, you many need to substitute the following technical names in the formula below:

 Voltage In (Vin)
This value is 5.0 for five volt UNO boards.
 LED Voltage (Vf)
See the LED manufacturer’s specifications.
 LED Current (If)
See the LED manufacturer’s specifications.

R = (Vin – Vf) / If

Long and short of all that technical mumbo-jumbo is, the onboard LED only uses a few milliamps (mA) of the 40 mA available on each ATtiny85 pin, leaving plenty of current for our use.

ATTiny85 / Digispark Connections

![The ATtiny85 chip connections](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/09-new-ir-testers.jpg)

The ATtiny85 chip connections

The numbers inside the rectangle are the physical pins of the ATtiny85 chip.
The numbers outside the rectangle are Arduino digital pin designations.
The A-numbers outside the rectangle are Arduino analog pin designations.

Digispark Clone Model Identification

Three models have been shipped. They have no feature differences, only a different connection for the on-board LED.

From the Digispark section of the Digistump Wiki . . .

| |
| --- |
| “You can identify your model by the presence of ‘rev2’, ‘rev4’, or nothing on the top (the side with the gold connectors) of the USB end of the Digispark. Also, there is a ‘rev3’ version in circulation; this is actually counterfeit (i.e. a clone which falsely uses the Digispark trade name), although functionally it seems to match the (true) revisions 2 and 4. ‘rev2’ or ‘rev4’ marking: The on-board LED is connected to P1. This board should cause no conflicts with any devices, but remember the LED is on pin 1 not pin 0! No marking: The on-board LED is connected to P0.“ |

Note: Most Digispark clones will have their on-board LEDs connected to P1. If yours is not the case, use 0 (for P0) in the #define you will add to the “Blink” sketch featured in Part Two of this article.

Putting it all Together

We can cleverly use all the gathered information and a couple of Arduino programming tricks to deduce a few shortcuts when building ATtiny IR Testers.

Sender Connections

The lead associated with the flat spot on the lens of the IR diode goes to PB0 on the sender board.
The other lead of the Diode goes to PB1 on the sender board.

![The IR LED attached](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/12-new-ir-testers.jpg)

The IR diode attached to the transmitter board

Receiver Connections

One lead of the IR transistor goes to +5V on the receiver board.
The resistor/transistor combined lead is associated with the flat spot in the lens, and goes to PB2 on the receiver board.

It’s a good tight fit for the other end of the 10kΩ resistor to go to PB0 on the receiver board.

![The IR transistor attached to the receiver board](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/13-new-ir-testers.jpg)

The IR transistor attached to the receiver board

Changing to Battery Power

The simplest way to power your tiny IR Testers is to employ the cable you will have used to program your board and a cheap 5 Volt battery bank.

Alternatively, a 9 Volt snap cap and 9 Volt battery can also be used.

![Adding a 9V battery connector](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/15-new-ir-testers.jpg)

Adding a 9V battery connector

When making these battery connections, put the snap cap’s RED wire to your board’s VIN connection and the snap cap’s BLACK wire to your board’s GND connection.

!The battery power connections

The battery power connections

Completing your Sender and Receiver

It is recommended you electrically insulate your little boards from possibly shorting to something. Some of you may want to go as far as to create your own custom 3D printed cases. Others may wish to cleverly employ clear heat shrink tubing. While still others may simply want to wrap all exposed metal in clear tape.

Programming

Please see the companion to this article to learn how you can program these boards with Arduino.

Sorry, Pinball News cannot provide Arduino coding or troubleshooting advice. However, there are many resources available for you that are listed at the end of this article for your convenience.

Testing

Once programmed and powered, the IR Sender and Receiver can be used to test each other.

Below you can see the IR Sender on the left and IR Receiver on the right, with power indicator LEDs glowing brightly, but on-board/built-in LEDs unlit while the boards are booting up.

![The powered IR Transmitter and Receiver boards](https://www.pinballnews.com/site/wp-content/uploads/learn/new-ir-testers/16-new-ir-testers.jpg)

The powered IR Transmitter and Receiver boards

Pictured below are the Sender on the left and Receiver on the right, this time with power indicator LEDs glowing brightly along with the on-board/built-in LEDs.

!The boards with their in-built controlled LEDs lit

The boards with their in-built controlled LEDs lit

Once you insulate your IR Tester sets, they will be ready to help you troubleshoot IR LEDs which are used as switches in many pinball machines. The receiver may also be used on its own to verify dead batteries in your television remote.

Resources

Parts Suppliers

Learning Links

Going Further

Pinball Repair Guides

This concludes the first, hardware-related half of this pair of Pinball News articles.

Please follow this link to view the second half, featuring the software details.**

_(Acquisition: raw_text, Enrichment: v1)_

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*Exported from Journalist Tool on 2026-04-13 | Item ID: f1552a1f-ac0c-413f-9e6a-f2ae482cad57*