Z80-MBC2 Build Part 3 – Final Assembly

Read Part 1: https://theclassicgeek.blogspot.com/2022/09/the-z80-mbc2-retro-homebrew-computer.html

 

Read Part2: https://theclassicgeek.blogspot.com/2022/10/z80-mbc2-build-part-2-uterm-vt100-style.html

Author's Website (Just4Fun): https://j4f.info/z80-mbc2 <--- Check it out! 

 

 Now that the Z80-MBC2 and uTerm are both up and running, it’s time to give it all a nice home. I went through several different ideas on how I wanted the final computer to look, from doing a full custom 3D printed case, to a small “all-in-one” keyboard style case like the Commodore VIC 20/64 “bread bin”, to something “boxier” to better fit 70’s era machines like the Altair, IMSAI, and SWTPC. The custom 3D printed case idea died very early on, I quickly realized I simply don’t have the time or skills to design and print a custom case that size, at least not yet. Perhaps I will revisit this idea in the future once I’ve honed my 3D design and printing skills further. The VIC 20/C64 style bread bin sounded great until I realized I couldn’t realistically find a case to fit my needs, in the size I wanted, at a reasonable price, and I had no desire to incorporate the keyboard into the final build. In the end I settled on a much more realistic and era appropriate “boxy” case that better represented machines of that era and the vision I had in my head. Also, this style of enclosure is much more readily available, inexpensive, and easy to modify. 

 

Buy Case: https://amzn.to/3FD9XgF

I really wanted the final machine to look like a “next step” for these early CP/M machines, with proper front panel buttons and lights. As well the keyboard port on the front panel for ease of use. On the back panel I put the SD card, power, VGA output, and the transparent serial connection so you could still connect to the computer that way if necessary. The last thing I would like to do is extend the GPIO to the back so it could be easily accessed, but that’s something I will tackle later since I haven’t decided exactly how I want to accomplish that. I’ll likely use a simple pin header that can connect to an external break-out board via a ribbon cable.

Here are a few things to note that may influence your own design choices, as it did mine…

1. Once you have the system setup how you like it, you’ll find yourself swapping the SD card out much less often, perhaps on the rare occasion you want to add something else you may have come across or if there’s an update released by the original Z80-MBC2 author. So having external front or back panel access to it isn’t necessarily a must, especially if your case is easy to open. I put mine on back for that reason, and because it’s a micro-SD and wasn’t sure if I could make the slot look nice enough to be front facing. Full size SD cards are easier to work with and I hate when I have to use my fingernail or a tool to insert and remove the micro cards.

2. I put the keyboard port in the front instead of the back purely for convenience. My system won’t be setup in the same spot all the time, and will get moved around quite a bit, so it made more sense to put it on the front panel. Also, since that’s where the port is on the uTerm, it just made it easier for the internal layout. I also used a PS/2 to USB adapter for ease of use since a majority of USB keyboards will work fine with this computer.

3. The transparent serial connection went on the back simply because it won’t get much use, but it’s still nice to have. I also went with USB type B because I prefer it over all the other port types. It’s more robust than its smaller counterparts and type B cables are still cheap and very abundant. I could have just used a pin header but incorporating the serial USB into the design just made things easier for later, especially since I have a few of these lying around and can spare one for this build.

Designing the layout and look of the front and back panels took quite a bit of time to get done and went through several different re-designs as the build progressed and I better realized how much space I actually had to work with. Getting it to look like it belonged in the late 70’s or early 80’s, with a bit of modern flare, wasn’t nearly as easy as I had thought. Once I was happy with the design however, it was just a matter of printing it onto sheets of adhesive vinyl to attach to the panels. The panels themselves had two options, drill and cut out the holes on the included panels or printing my own. In the end I decided to print my own to give me more 3D design practice, and it guaranteed a good fit. 

 

The inside layout was also a bit of a challenge, I wanted it as “clean” as possible, but I also had a very limited amount of space to work with. I had to extend everything to the front panel while trying to maintain the ability to easily disconnect everything if necessary. I thought about designing a custom front panel PCB, but I really didn’t want to wait for it to arrive and I wasn’t sure I could make it cleanly fit. So, I decided to just extend everything directly using pin headers. It makes it easy to replace anything that may go bad and it fits into the limited space. I also think it fits better with the overall aesthetic of the machine since many of these early home computers had a lot of DIY modifications.

Mounting the PCBs was accomplished using a custom 3D printed support structure that I designed to hold everything in place, but still allow for easy servicing should the need arise. The Z80-MBC2 and uTerm are both held in place using screws, and the SD card and RTC are held in place using 3M double sided mounting tape. The base of the support structure is screwed to the case, and the two upper sections are sitting on top of 6 removable 3D printed standoffs. It’s not perfect, but the overall design fits in the limited space, holds everything in place, is easy to disassemble, and it looks the part of a homebrew computer.

 

The final result pretty closely matches what I think a “next step” homebrew CP/M machine like this would look like. If nothing else it appeals to me, and that’s really all that matters. I love how it looks and it has given me the opportunity to explore an era of computing that I missed, even if only a little. The question now becomes, what to do with it? Will I actually use it? The short answer is yes, I’ll definitely use it. 

More photos coming soon!

One of the reasons I wanted the Z80-MBC2 was to learn more on how these old machines worked, and since their so simple, they’re easy to learn on. I enjoy messing around with the old software and games, and it can actually still be useful, but that’s not the real point. Sometimes the best part of a trip is the journey, not the destination. Most people will look at old retro machines like this and think “what’s the point?”, and if you have to ask that question, then I’m not going to be able to explain it to you. That simply means this isn’t your thing, and that’s fine, we’re all different, but if you’ve made it this far through all 3 long winded articles, then you probably already understand.

I had a great deal of fun building this machine, I learned a lot along the way, and ended up with a neat little retro computer that will provide me with countless hours of entertainment. From here I will be doing a follow-up article to cover more of software side of things, changes that may have been made, and share why I think an old-style homebrew computer like this can actually still be fun and useful. For now though, I’m just going to enjoy the fruits of my labor and say thank you for taking the time to read through all of this. I hope you found something helpful here, or if nothing else, it was entertaining. 

Read The Build Follow-Up - What Can It Do?: https://theclassicgeek.blogspot.com/2022/12/z80-mbc2-build-follow-up-what-can-it-do.html

Simple and Inexpensive DIY Electronics Project Power Supply

When I started diving back into electronics a couple years ago, after my long hiatus, one tool I knew I was going to need was a variable power supply. At first, I was looking at just buying a standard bench power supply, they’re relatively inexpensive and would provide more than enough juice for the small low-powered devices I would be building or repairing. In fact, they were a huge overkill since most all the devices I work on run off 12V or less and draw so little power, many designed to run off 5V or battery. The other drawback was the fact I don’t yet have a dedicated workspace for all my projects, meaning I have to setup and tear-down my workspace when I need to work on something, so size and space is a concern.

Those factors lead me to look for an alternative solution, which landed me squarely in buck-boost converter territory. Small inexpensive DC to DC converters that can either boost or reduce an input voltage. I’m not going to go into a great deal of detail on the devices themselves, but you can check out this Wikipedia article on them if you’re curious. Since my power needs are currently so small, a decent buck-boost converter with a decent power supply to feed it is all I need, so that’s the path I chose.

From the start I knew I wanted two of them, a small “portable” one I can also use as a backup, and a somewhat larger more convenient one to use much more often. The small portable one was easy, I just bought one on Amazon from a company I already knew and trusted, Drok. I have used some of their buck converters in the past and all of them worked perfectly, so I picked up the model you see below. It’s more than capable of handling anything I would ever be using it for, inexpensive, and small enough to fit in my electronics toolbox. 

 

Buck Boost Converter: https://amzn.to/3tkr0i1

For my “project power supply” however, I wanted something a bit easier to use, and decided I would just build something simple around a buck-boost converter that I could quickly and easily adjust, connect and disconnect power, monitor power usage, and that I could mount in an enclosure but not take up a lot of space. I had originally wanted to buy a Drok unit like above, but they were sold out at the time, so I ended up going with a lesser-known seller, but it still worked just as well. The converter from “TXKEC” you see below is when I ended up buying.

Once it arrived, I tested it out to make sure it was working as intended and then looked for an enclosure to put it in so I could wire up a couple terminals, a power switch, and a barrel jack so I could use a standard brick power supply to run it. Lucky for me, I already had one on hand that ended up working out perfectly!

 

Enclosure: https://amzn.to/3UvRqsG

Buck Boost Converter: https://amzn.to/3fJ0cVb

Drok Buck Boost Converter: https://amzn.to/3FNI6Ml

For connectivity, I added a single banana plug style screw terminal and a single spring-joint clamp terminal. Like I said above, this will only be used on very low powered devices at 12V or less, so I don’t need anything “beefy”. For the power input I used a standard 5.5mmx2.5mm barrel jack so I could use many standard brick power supplies, with the one I chose being a 12V 36W 3A model, way more than I will ever need on this thing. From there I just had to modify the case to fit everything, add a power switch, wire it all up, make a couple cables using banana plugs, and make it all look nice. The end result is what you see below. 

This was a very simple build to perform a very simple task. For the low powered devices I work with a vast majority of the time, it’s all I need. It works perfectly and allows me to easily select the desired voltage, monitor the input output voltage, as well as the output current, power, and capacity. Using the two terminals I decided to go with means I can easily connect it up to just about anything I need. 

Overall, I’m very happy with my little “project power supply”. When the time comes and I need more power or more control, such as with classic computer repair or higher-powered devices, I’ll invest in a proper bench power supply, until then, this little guy is all I need.

Thanks for reading!

 

Z80-MBC2 Build Part 2 – The uTerm VT100 Style Terminal

Read Part 1 First: https://theclassicgeek.blogspot.com/2022/09/the-z80-mbc2-retro-homebrew-computer.html

 

Project Source: https://hackaday.io/project/165325-uterm

Author's Website (Just4Fun): https://j4f.info/z80-mbc2 <--- Check it out!

The next step in building my idea of a “modern retro CP/M & BASIC computer” is building the uTerm. A VT100 style terminal for the Z80-MBC2 that gives it the ability to act more like a stand-alone computer. The uTerm would be the modern equivalent of a classic terminal you would have used back in the 70’s and 80’s to connect to a machine like this, allowing you to hook up a keyboard, monitor, and 9V power supply instead of having to use a serial connection to an existing computer, though that feature is still maintained via a transparent USB serial connection on the board.

The uTerm uses a standard old-school PS/2 style keyboard port, but most standard keyboards should still work with a simple USB to PS/2 adapter.

NOTE: 60% keyboards may not work, I have 2 of them I use for other tasks and neither worked on the uTerm. However, every other “standard” keyboard I have, including 10-keyless, worked fine.

It also uses a D'SUB VGA connector for the video, but here again adapters can be used to connect to displays that may not have that connection available. The best part about the uTerm is the fact you no longer have to use a terminal emulator, like Putty, to use the Z80-MBC2. It outputs a 30x80 column display and even has the ability to set the text color to either white, green, amber, or cyan to complete the retro feel of this machine.

Just like the Z80-MBC2, the build is pretty straight forward, there is bill of materials and schematics included that spell out all the components you need and where they go. All you have to do is track down the components and solder them into place according to those documents. Just like all builds, it’s good practice to test the components you can before using them in your build.

To make things even easier, you can buy the PCB on eBay for around $15 that already has the surface mounted STM32 chip pre-programmed, saving you one extra step if you don’t already have the necessary tools to flash the chip or ae not comfortable with SMD soldering. All the other components are relatively inexpensive and easy to find on Amazon, eBay, and other sites. Just like the Z80-MBC2, I already had most of the parts on hand, making the build even cheaper.

If you can't find the specific heatsink used in the authors build, that's not a problem. Any standard heatsink that fits the LM7805 and covers the entire regulator back, as seen on mine, will work just fine. It does get warm, but dropping 9V to 5V on such a low drain device doesn't produce enough heat to cause any problems using a smaller heatsink. If you have thermal pads or paste you can use, that helps as well.

 

The same advice for building the Z80-MBC2 also applies here, and I have compiled a list of links to all the parts you need on Amazon and eBay to help you along, and most of them are the ones I actually used. 

 

• 100uF 16V Electrolytic Capacitors: https://amzn.to/3RoNEiA
• 100nF Ceramic Capacitors (Need 6): https://amzn.to/3Ef7vxV or https://amzn.to/3fky5uY
• Kit with all necessary ceramic capacitors: https://amzn.to/3ClW6d8
• 3MM LED Kit (All the necessary colors): https://amzn.to/3Rqm9p0 (Should have left over from Z80-MBC2 build)
• Tactile Momentary Button Kit: https://amzn.to/3rkjvXc (Should have left over from Z80-MBC2 build)
• 1N4001 Diodes: https://amzn.to/3CMJBZo
  
• 1N5817 Diodes: https://amzn.to/3ROa4Kw
• 5.5x2.1 DC Barrel Jack: https://amzn.to/3T94pQ5
• PS/2 Keyboard Connector: https://amzn.to/3VbJRZj
• VGA Connector: https://amzn.to/3ywh1Jn
• 2N7000 Transistor: https://amzn.to/3COh4CV
• 2N3904 Transistor: https://amzn.to/3Ey4pFu
• L7805CV 5V Voltage Regulator: https://amzn.to/3CMLc1k
• LD1117V33 3.3V Voltage Regulator: https://amzn.to/3CMLo0y
• 25MHz Crystal Oscillator: https://amzn.to/3fVA49v

 

eBay Search for 74HCT00 NAND Gate - Note that it must be a 74HCT00N NAND Gate IC, any brand will work. Buy from sellers in the USA (or your local area) when possible to increase your chances of getting "good" parts. It  also makes it a lot quicker and easier to not only get your parts, but do returns if necessary.

eBay Search for uTerm PCB - If the PCB with the pre-programmed STM32 chip is still available, I suggest getting that one. If not, it simply means you have to buy the STM32F030F4P6 surface-mount chip yourself and program it. However, as of writing this article (October 2022), the STM32 chip is nearly impossible to find, so you may have to really look to find one.

Here is a socket kit I have not used, but contains all the necessary sizes: https://amzn.to/3E5tuaz 

I did not include individual links to all the resistors because these are really easy to find and have a pretty wide tolerance, and it’s somewhat difficult to get resistors so far out of spec you can’t use them when a project like this gives you a 5% tolerance variance. Many "cheap" resistors that claim they are within 1%, are actually 2-3%. Either way, for this project and many others, as long as you buy ones that say 1%, you’re generally safe.

Amazon Search 1/4 Watt Resistors: https://amzn.to/3SCccGt

Also, there are a lot of good resistor assortment kits sold on Amazon, and many contain almost all the ones you need for the Z80-MBC2 and uTerm, so you will only need to buy a couple values separately. Just remember 5% (shoot for 1%) and ¼ watt and you’re good.

In the bill of materials, they list 4k7 and 2k2 resistor values, this is just another way of writing 4.7K  ohms and 2.2K ohms.

For the LEDs, be sure to use the colors indicated, or other colors with the same forward voltage value. This is talked about on the project page as well.

If you bought the PCB with the pre-programmed STM32 chip already installed, then there really isn’t much more required once you have it all assembled, other than using the jumpers to select your color choice.

If you bought a bare board and the STM32 separately, then you’re going to have to solder the chip to the board, fully assemble the uTerm, and then flash the chip before you can use it. A programmer is needed to do this, but thankfully they’re cheap and easy to find on Amazon. The full instructions on how to do it are covered on the project’s homepage, linked above and below.

Programmer: https://amzn.to/3SOjk2o

How to Program the STM32: https://hackaday.io/project/165325-uterm/details 

(Scroll down to "HOW TO FLASH THE STM32 WITH THE ST-LINK V2" at the link above.)

 

Using the uTerm is easy. To power both the Z80-MBC2 and uTerm, all you need is a 9V power supply, a PS/2 keyboard or USB to PS/2 adapter and just about any USB keyboard, and a standard D'SUB VGA cable (and an adapter if you don’t have a monitor that accepts the VGA input). If you’re connecting the uTerm to the Z80-MBC2 directly, you don’t need the supplemental power cord running between the uTerm and Z80-MBC2, but if you’re going to run it detached the supplemental power connection is highly recommended. Mine has been slightly altered to better fit into my final case design. If you're using the supplemental power between the uTerm and Z80-MBC2, ensure you have the polarity correct before powering it up! Also, the 9V power supply must be center pin positive!

You don't need a beefy power supply, in fact, it will even run off a 9V battery for a while if necessary. As you can see from the photos, I'm powering mine using a simple DIY power supply I put together to test small 12V or less projects, that also allows me to measure usage information.

Here are some power and temp numbers running under load. Using ASCIART.BAS and LOG10K.BAS as benchmarks. Readings taken from my PSU and IR thermometer. Temps taken after 30 minutes of operation at idle and then under load at around 70F (21C) ambient.

Standard Keyboard (No Backlight): 0.090 to 0.100A / 0.81 to 0.105W max draw - Around 100F (38C) on the LM7805, hovering around 98F.

Standard LED Backlit Keyboard: 0.255 to 0.265A / 2.25 to 2.40W max draw - Around 110 to 115F on the LM7805, hovering around 111F (44C).

Note that the power draw and temps are affected by your choice of keyboard, however the numbers are so small it really doesn't matter much as long as your 9V source can provide the power needed. The temps using the smaller heatsink are also well within the safe operational range of the LM7805 voltage regulator. Remember, these voltage regulators work by dissipating the excess voltage as heat, and you generally don't want to operate electronics anywhere near their max operational temperature. The LM7805 can handle a lot of heat, but the max temp often used for safety is about 110C (230F), and we never go over 46C (115F). So this system stays nice and "cool" by LM7805 standards.

Once you have it all hooked up, just power it up and enjoy! I'm not going to cover troubleshooting in any detail for the same reason as on the Z80-MBC2, not enough time. However, if it's not working, make sure all the connections are hooked up correctly and securely, check to ensure you have the correct input selected on your monitor, and press the “Reset” button on the uTerm to see if that helps. You can also check the jumper settings for the color selector. If all else fails, hook the Z80-MBC2 back up to your PC using the USB serial adapter to ensure it's working. Note that there are test points on the uTerm PCB if you know how and need to use them, labeled as TP1, TP2 etc.

There's also a modified firmware version available that adds a few more options you can try if nothing else is working, or you can re-flash the original firmware if you have the programming tool to do so. 

Modified Firmware: https://gitlab.com/luckynate4/nuterm

My uTerm fired right up and has been working just fine. Since building the Z80-MBC2, I has since settled in on using CP/M 3 and have grown quite attached to the classic green text. The Asus monitors I use have legacy VGA inputs and have the ability to run that input at 4:3, so it's about as “authentic” as you can get using modern hardware.

Now that I have the uTerm all setup and running, the final step is to cram it all into a case that does the build justice, completing the “modern-retro” look I want for this cool little Z80 computer.

I did print the brackets the author included, the flat (horizontal) mount version, just to see how they worked, and they print just fine on my Ender 3, as you can see. The print time is about 5 1/2 minutes per bracket.

 

I will be using a pre-existing enclosure and modifying it to fit my needs for the final build. I had considered 3D printing a full custom case, but to be blunt, that’s a little outside my 3D design capability at the moment considering the overall size, however I have found a couple cases I can easily modify and 3D print only the parts I need to complete the build.

Thanks for reading and I’ll see you in the 3^rd and final part, where it all comes together!

Read Part 3 - The Final Assembly: https://theclassicgeek.blogspot.com/2022/12/z80-mbc2-build-part-3-final-assembly.html

 

 

Programming Tools for the Atmel ATtiny85 and ATmega328P

 

Just about every project I do that requires a micro-controller is powered by either an Atmel Tiny85 or Mega328. The ATmega328 is of course the chip that powered the amazingly popular Arduino Mega, Uno, and Nano boards. Where as the ATtiny85 is what powers cool little boards like the DigiSpark and Adafruit Trinket. The Atmel company was absorbed by the Microchip Technology company in 2016, but the branding for many of Atmel’s chips remain mostly unchanged, though there is some misinformation floating around regarding some of the codes used to identify specific chips.

The biggest issue I see in online reviews, and a few other places, concerns the “P” identifier, such as in the ATmega328P-PU chips used on Arduino boards. The P before the dash indicates it’s a “Pico Power” version meant for low powered circuits, but the P after the dash simply indicates the package type and means “Plastic”. The problem is there are also ATmega328P-U chips used on Arduino boards and available for purchase, leading people to think these were fake because they don’t show up in official Ateml datasheets. The same goes for the ATtiny85-20PU vs ATtiny85-20U, the info AFTER the dash has nothing to do with power, but many people believed the P in 20PU meant “Pico Power”, when in reality it only means “Plastic”, just like on the Mega328.

The issue arose because at some point Microchip decided to drop the package type identifier, meaning the ATmega328P-PU became the ATmega328P-U and the ATtiny85-20PU became the ATtiny85-20U. Just in case you’re wondering, the “U” indicates the operating temperature range of the chip, -40C to +85C. So, the “PU” and “U” chips are all the exact same chip, the ones without the “P” after the dash are simply newer. 

In case you’re wondering, even I was a bit confused at first when I had ordered a couple tubes of both chips before they became almost impossible to find, so I reached out to Microchip and they got back to me explaining everything I just passed onto you. So, if you’re shopping for these chips, I hope this helps clear up any confusion. 

 

Moving on, before I decided to forgo using Arduino Nano units to power all my projects, and just use the chips themselves, I had stocked up on a few sets of Elegoo Nano units (and before prices went crazy), so many of the prototypes you see on here will be powered by those Nano units instead of the chips. When I did make that change, I also had to decide how I was going to write the necessary bootloader and whatever data I wanted to the chips, and that’s what I am covering here. This won't be a tutorial, there are plenty of good ones out there already, this is just a quick overview of the tools I use to get the job done.

 

Starting with the ATtiny85-20U, I decided to keep it simple and ordered a Tiny AVR Programmer from Sparkfun. They are compatible with both the Tiny85 and Tiny45 chips, are convenient USB sticks, and can connect to the chips either via the included socket or via jumper wires directly to your project. It’s fully compatible with the Arduino IDE that I’m already familiar with and works fine in both Windows and Linux (Ubuntu 20.04 in my case). Getting it up and running is incredibly simple and Sparkfun provides full easy to follow instructions on their website to guide you should you need it. I highly suggest reading it!

Learn: https://learn.sparkfun.com/tutorials/tiny-avr-programmer-hookup-guide/

Buy: https://www.sparkfun.com/products/11801 or https://amzn.to/3PbgP7U

Next, I decided to put an extra Arduino Uno I had lying around to use as the programmer for my ATmega328P-U chips. So I ordered a simple DIY "Canaduino" Arduino Shield with a ZIF socket from a company called Universal-Solder, so I could quickly and easily program my chips and put the extra Uno to use. Again, it’s quick and easy to build and get working and I can still use Arduino IDE since all this does is allow you to move the ATmega328P off the Uno and to the ZIF socket.

Buy: https://universal-solder.ca/product/canaduino-zif-socket-arduino-programming-shield/ or https://amzn.to/3dlX6VO

 

Both of these tools allow me to quickly and easily program both the Tiny85 and Mega328 chips I use in almost all of my projects. Doing it this way saves space and money when compared to using an Arduino Nano like I was in the beginning, and gives you more control over your final circuit design.

The ATtiny85-20U and PU, and the ATmega328P, can run between 1.8V and 5.5V. Also, depending on your specific needs and setup, you can run them without a clock crystal. When I use the Arduino Nano, they are all powered using a 9V battery, the Nano's built in regulator steps the voltage down to 5V. When I just use the chips themselves, I can use 2 or 3 AA or AAA batteries, depending on the demands of my circuit as a whole. If my circuit still needs more power, I can use a simple L7805 voltage regulator and a couple smoothing capacitors to supply 5V from a 9V or other battery, depending on my needs. 

If you're going to be programming a lot of ATmega328P or ATtiny85 chips, then I highly recommend one of these tools, or something similar. They made the process easy and save a lot of time.

Thanks for reading!

Paranormal Tool DIY - The REMPOD

A REMPOD is device that emits an electromagnetic field, and when that EM field is altered, emits sound and/or lights to indicate a disturbance in the force. If this sounds familiar, then perhaps you’re aware of a musical instrument known as a “Theremin” that does this very thing. Invented in 1920 by Leon Theremin, the player uses their hands to manipulate the EM field generated by the device to produce musical tones. Fast forward to the 21^st century and this same concept has been adopted for paranormal research, branded as the “REMPOD”, and popularized by shows like Ghost Adventures.

Many of those in the paranormal community believe spirits have the ability to produce and manipulate electromagnetic fields, and that this would allow their presence to be detected using something like an EMF Meter. EMF Meters are a common tool used in many professions and have long been used in paranormal research as well, with the classic “K2” being one of the most popular for many years. The problem with an EMF Meter is it requires the presence of an EM field, so a spirit would have to generate one strong enough to register on the meter, and many of those in the community believe not all spirits are strong enough to do this. Enter the REMPOD.

Since a REMPOD is basically just a miniaturized modern Theremin, it produces its own EM field, and so it’s theorized a spirit can manipulate that EM field much easier than trying to produce one themselves. This would allow researchers to communicate with spirits, and detect their presence, much more reliably than with an EMF meter alone. At least, that’s the theory.

I’m a skeptic by nature, and while I find paranormal research fascinating and entertaining, my logical brain often gets in the way of actually believing the “evidence” often captured using devices like this. The thing about EMF fields is they exist everywhere, even in the absence of man made electrical devices, they’re produced by forces in the Earth and all around us, and in wildly varying intensities. EM fields are very easy to manipulate, they’re not all that stable in nature, and are subject to interference. Meaning that just because you detect a random EM field somewhere there is no electrical power, does not mean it’s a ghost. The same goes for a REMPOD, its own EM field can be interfered with and “detect” the presence of electromagnetic waves, but it can’t tell you where those waves are coming from. It could be from the Earth itself, the radios many investigators use, or even from sources outside the sphere of their investigation. Basically, our world is flooded with electromagnetic waves, so saying a detection by a device is a ghost just don’t sell it for me.

That all being said, many paranormal investigators use multiple different tools to try and collaborate what they see, hear, and detect. So, it’s really all down to what you believe. Personally, I don’t have to believe in it to think it’s cool and respect those who do. As well as those who are genuinely trying to prove the existence of the paranormal or help people.

Now, let’s get down to the REMPD itself. They have been around a while now, and have gone through changes and upgrades, but their all basically the same thing, a Theremin circuit. The original, as seen in the tear-down photo shared below from “Skeptical Enquirer”, is literally just a modified “Junior Theremin” DIY soldering kit from a company called MadLab. While some later versions are custom similar circuits, they all still do the same thing. Thankfully, these kits are still available for around $20 or less from various places, meaning you can modify one yourself to make your own custom REMPOD! 

 

Buy: https://amzn.to/3cPzIjh

This Theremin circuit is really simple, powered by a 555 timer and 12C508 micro-controller, supported by the necessary capacitors, resistors, a voltage regulator, LEDs, speaker, antenna, and power inputs. Meaning, it would be easy to duplicate using something like an Arduino or more common Atmel Micro-controller. MadLab even made the code on the 12C508 available for anyone to use, or modify, but that’s a bridge I will cross later. For now, we’ll stick with the original and modify it to fit our own design. I'm not trying to hide what's inside and I want it easy to duplicate. 

 

I wanted to keep our REMPOD prototype as small and portable as possible and have a simple on/off switch. I also want to keep it easy to service and modify later, so I won’t be encasing it in resin or glue, but I may use a little in the prototype to hold things in place.

One future alteration I will be making is a custom 3D printed housing, but since I haven’t designed one yet, a small basic project box will do for our prototype, and it will make it easier to design an enclosure later. With this in mind, I built the circuit, extended the LED, speaker, and power connections. Once I verified the circuit was working correctly, I made the necessary quick and dirty alterations to the project enclosure and crammed everything inside, using a bit of hot glue to keep things from moving around.

Now that our prototype is complete and fully functional, I can honestly say it seems to work quite well. My wife will be able to use her custom, and considerably cheaper, REMPOD to hunt ghosts. Along with the other tools I have made for her, she’s almost got as many tools as the pros on TV. She’s happy to have another tool for her hobby, and I’m happy to make them for her since that’s my hobby! 

 

Now, it's time to work on getting that custom enclosure designed and printed, it's almost done! Here is a snapshot of what I got so far. I'm new to 3D design, so I'm still getting the hang of it.