Introduction: " Tachyscope CRT " a POV Display Project
This project consists of using a micro-mini CRT and spinning it to create a 3D "Holographic" audio oscilloscope effect display.
Sorry for the 'fuzzy' images, camera sync issue.
Supplies
Major parts used,
A- video camera Viewfinder ( for CRT display and driver PCB).
B- Wireless Audio video Sender and Receiver ( I used an old Baby monitor)
C- custom made wireless DC power link, ( an air core transformer ) , 2 hand made coils, and driver circuit.
D- DC motor and PWM driver for rotation of platter.
E- 2 pulleys and O ring as a drive belt. Bearings, support shaft, flange.
F- large plate (plastic?) for mounting all the bits.
Step 1: Testing the CRT With Video
The Viewfinder PCB needs 5vdc and composite video to operate , after researching the main IC AN2501S circuit , (locating a Panasonic NV-Me crt viewfinder schematic ).
found here: https://www.experimental-engineering.co.uk/wp-content/uploads/2016/11/EVF_Schematics.png
With this POWER (+5v) and Video IN connection points where located. With continuity meter I traced the 5v to pin 2 of the IC, and video IN pin 18.
Feeding composite Video to confirm the CRT displays properly.
Step 2: Changes to Make CRT an Oscilloscope
Using the CRT as a simple AUDIO oscilloscope,
- On the CRT YOKE identify the HORIZONTAL and VERTICAL coils, label the 2 pairs (4 wires), in my case red and blue are HOR, green and yellow are VER.
- Cut all 4 wires from the PCB, keep in mind that you need to re-solder them later. hint Document where the wires came from on the PCB.
- Reconnect (MOVE) VER wires (green/ yellow) to HOR coil wires. In effect we just moved the driver for VER to control the HOR coil.
- The HOR wires, blue and red from the PCB are not used. leave disconnected on the PCB.
- The Audio amp is wired up to VER coil ( Yellow and Green wires) on yoke.
- Audio Amp see schematic in OSCILLOSCOPE.PDF file below. NOTE, the VER coil is wired up in Parallel with the speaker, (optional) if you want to hear what is displayed.
Attachments
Step 3: Changes to Make CRT Into a 3D Visual Effect
This part of the project is what is displayed in the intro , A 3D Audio Oscilloscope effect, using the CRT for displaying sine waves while rotating the platter.
IN NO PARTICULAR ORDER
Step 1 Mounting the CRT and driver PCB to platter ( green plastic plate).
Step 2 Mounting the Audio and Video receiver . ( some of you might notice the 4 AAA batteries, this was done on my prototype before the DC wireless was installed)
Step 3 Mounting Wireless DC power transfer, custom made air core transformer. How I made that in the next chapter just below.
Step 4 Mounting the bearings and support shaft.
Step 5 Motor / drive circuit.
Attachments
Step 4: Wireless DC Transfer Circuit / Build
In this part, How I built the DC power transformer, ( air-core), how to get 12v DC to 12v DC without wired/ physical link/ slip rings.
Part 1PRIMARY coil
(1) label tail 'A' , 10 turns of # 20 awg copper shellacked wire. Wrapped onto a 2" diameter ABS black pipe.
(2) label tail 'B", this is the CT , "center tap".
(3) another 10 turns, spooled on the same direction, label this tail 'C'
Optional to encase the coil in Epoxy or resin, I did Epoxy.
Part 2 SECONDARY coil
This one is a little more involved, as the secondary coil was made very flat- skinny.
To do this I used 1 pair a disk platters from an old 5" hard drive, contact glued a waxy paper to each disk on the sides facing each other.
Found a metal washer as a spacer for my desired coil thickness. The wire will be wrapped around the circumference of the washer.
Drilled a hole in one of the HD platters for which wire labelled 'D' will protrude from.
The washer will be "sandwiched" between the 2 HD platters. then add the resin / glue.
Start
(1) Prepare the 2 HD platters by glueing the waxy paper to the one side of each disk (platter) with spray-on contact glue
Position the washer in center of the disk and drill 1 hole for wire 'D" to exit from.
(2) Pre-add the resin or epoxy to the inside surfaces of each platter, dont use 5 min epoxy, it will harden before you can finish the whole process of spooling the wire.
(3) With the wire tail labelled 'D' already in the hole, install the 2nd platter and create the "sandwich". I found it almost impossible to try and fish the tail 'D' into the hole when both platters where bolted together. Hence why I did it at this point.
(4) Wrap 30 turns of # 20 awg wire to the sandwich spacer (core).
add more glue if / as needed, I used a drill to slowly rotate the sandwich to prevent the resin/ glue from draining out.
(5) Once cured, separate the 2 platters and clean up the edges of the coil.
(6) label the last wire tail as 'E', the secondary coil wires should be D & E. as per schematic.
(7) Mount / secure the coil to the nylon "O" ring pulley, I also added a small 2 pin connector .
(8) The Secondary coil does the "spinning", and the Primary coil is "static".
(9) Adjust the clearance (gap) of the 2 coils for as close as possible without touching, I used the thickness of a sheet of paper as a guide.
Done the fabrication of the coils.
Step 5: Wireless DC Power Circuit Build
In this section , the assembly / build of the DC Wireless electronics circuit.
from STEP 3, refer to the TRANSFORMER 1.2 PDF attachment .
Its pretty much self explanatory , in short I use a Mosfet K1351 to drive the coil ( primary). 12vdc power IN. R2 is optional. I found it worked with or without it, I got better results without it.
The K1351 needs a good heatsink, I also added a fan for good measure.
The secondary outputs 12v under load. I use 12v for the Baby monitor electronics. With this baby monitor I use the Video and Audio circuits.
The 12v is then fed to a 7805 regulator to feed power to the CRT logic/ pcb.
If using the Tachyscope as an Audio Oscilloscope, I make use of the Audio from the baby monitor, If wanting the show Video on the CRT ( when NOT spinning the platter) then I switch to the Video of the baby monitor.
Misc notes,
Before using the baby monitor, for driving the VER coil of the CRT with Audio I used a TEA2025 audio amp IC and a Bluetooth receiver, worked extremely well, problem was I had no Video source, hence the baby monitor, it had both audio and video outputs.
Works great in a LOW light environment.
This project isn't very practical but fun to see the sine wave in a 360' image.
Still pondering If I will add this to my NVictria Steampunk project.
Again apologies for the choppy video here, can only do so much on a cell phone [:(
If you have any questions, fire me off a comment.
Thanks for reading
Daniel Ross
Aug 2023
PS Youtube video, under "TACHYSCOPE CRT", link here.
Participated in the
Unusual Uses Contest
