Science Buddies: "Ask an Expert"

Hello,
We try to create a wire recorder according to the page:
https://www.sciencebuddies.org/science-fair-projects/project-ideas/Elec_p015/electricity-electronics/recording-on-a-wire

Parts used in the project:
Cart wheels:
13 x 2-1/2 in. Rubber Wheel
https://www.princessauto.com/en/detail/13-x-2-1-2-in-rubber-wheel-assembly/A-p8787533e

Audio amplifier A:
Lepy LP-2020A
https://www.amazon.ca/Lepy-LP-2020A-Class-D-Amplifier-Supply/dp/B00V9AYMZ4

Audio amplifier B:
https://iliveelectronics.com/cd-g-karaoke-with-dock-for-ipodr.html

Signal amplifier:
Pyle PP999
https://www.amazon.ca/PYLE-PP999-Phono-Turntable-Preamp/dp/B00025742A

Ferrite bead core:
0.5 MHz to 20 MHz
Inner Diameter: 0.187 inches
Outer Diameter: 0.375 inches
Height: 0.125 inches
http://www.amidoncorp.com/ft-37-75/

Magnet wire:
MAGNET WIRE 34AWG 0.16MM 210GR
http://sayal.com/STORE/View_SPEC.asp?SKU=231821

Hookup wire:
24 GA Stranded wire

Recording wires:
40 GA Stainless Steel Wire https://www.kbeevapes.com/product-p/ss316l_40.htm
38 GA Stainless Steel Wire https://www.kbeevapes.com/product-p/ss316l_38.htm
28 GA Steel Galvanized Wire https://www.canadiantire.ca/en/pdp/hillman-28-gauge-galvanized-wire-100-ft-1610720p.html
24-GA Galvanized Steel Wire https://www.homedepot.com/p/OOK-250-ft-x-24-Gauge-Galvanized-Steel-Wire-50137/100144004
19-GA Galvanized Steel Wire https://www.amazon.com/50132-Gauge-50ft-Steel-Galvanized/dp/B001EX584A

Setup:
We made 4 Ferrite bead cores with ~220 turns (with 10 turns give or take). The gap in the core is created by using a diamond wheel (https://www.dremel.com/en_US/products/-/show-product/tools/545-diamond-wheel). Each core has 5 ohms (0.4 ohm give or take) resistance.

For recording scenario, music from the cell phone (headphone jack) to RCA input of the amplifier (audio amplifier A). Then pickup wires are used to to connect from Left channel speaker out to the magnet wire ends. The measured voltage is about 1.1 volt from the speaker out.

For playback scenario, core' magnet wire is connected to pickup wires then converted to a RCA jack input to a signal amplifier then to audio amplifier B.

Since we have 4 cores, we test each pair by put them close together and we can hear music from amplifier B when playing thru amplifier A. Even when the two cores is 3 inches apart, music can still be hear from amplifier B. This ensure us (if we are not mistaken ....) that all 4 cores are working properly.

The obstacles ......
As you noticed we listed a few type and GA size of the recording wires.We tried them all with different speed and with/without distance(touching) from the core to the recording wire, we have no luck on playback. All we get during playback is static noise when the wire running against the core and no sound when the core has a distance with the recording wire.
We also suspect if the signal is too week in the wire, that is how the signal amplifier kicks in to the project, but then again no help on that. Also from one of the searched post, a person suggest by turning the core 45 degree so each core leg to contact with the recording wire, that did not bring any success to us.

The questions we have is how do we sure the wire is magnetize (material recorded) after passing thru the core? We test by use a compass on top of the wire, the direction did change, for example it will make the needle point to North East when it suppose to pint to North.

We are running out of idea of trouble shooting, any suggest will be a great hint for us to move forward.
PS We tried to attach the pictures of our set up .... we cannot upload jpg files or zip file
Thanks in advance.
Mandy

Hi Mandy,

From your description it sounds like you've done a great job building your wire recorder. I don't have much experience with this topic but I will try to help. And perhaps some others with more expertise in this area will chime in.

Based on the testing you described it seems to me that either the recording signal is too weak or the signal isn't being transferred to the wire.

You might try increasing the gain (volume control?) on amplifier A to get a stronger signal (more voltage) to the recording head.

Although the wire types you listed may work, you might want to try recording wire as described in the project procedure. That way you'll be certain that the wire works.

I'm assuming that you've built your recorder with separate recording and playback heads (I'm not sure why you have 4 cores). You might try using just one head for recording and playback (as described in the procedure) to simplify your troubleshooting. Once your record head is working you could put the separate playback head and amplifier back into the system

I hope this helps. Please ask again if you have more questions.

A. Norman

Hi,
Thank you for the suggestions!

We did try the increase volume/voltage scenario. We actually have a amplifier C that was not listed in the picture on our first post, namely our home theater amplifier (100 watt per channel). When we set the volume to half of the maximum in the recording scenario test ....smoke comes out from the core and the core is burning hot. We suspect it is the Enamel insulation from Enamel-coated Magnet Wire which "melted" during the instance. We did not get enough time to measure the voltage from the speaker-out, but we did measure the core's resistance after the instance and it went down from 5 to 3.x ohms. I suppose we could have re-think the Ohm's law before the attempt. Luckily the home theater amplifier has a overload protection and no damage is done on that test.

The reason we have 4 cores is for back-up purpose. We labeled them and only use "Number 1" core. The rest are put aside for backup purpose because it takes time to slice a core gap, coil the core, file the enamel from the magnet wire plus solder/heat shrink the connections.

From your suggestion "Once your record head is working", this is one of the nuts we need to crack. Correct me if I am wrong, we tested the scenario of 2 cores side by side, one core for broadcasting and the other one for receiving. The result is, the broadcasting music can be heard from the receiving core connected to a amplified speaker, does that mean the core is creating magnetic fields/waves? If so is there a way you can suggest to measure the charges created in the core tips, and how strong do we need for writing to the wire? That is why we have the question in our first post on how can we tell if the wire has "the recorded data" or not ..... this is our main blocker.

We also tried to source the "vantage recording wire", they are quite pricey when considering the shipping cost to Canada (we currently monitoring the ebay deals). That is one of our open leads to consider as the last resort.

We are appreciated your suggestions and thank you again for helping us.
Mandy

Hi Mandy,

It seems that amplifier C put out a bit too much signal! Based on that experiment I would say that you ruled out weak signal to the recording head as a problem.

The “side by side” test that you described is a good demonstration that both broadcasting and receiving cores and the associated amplifiers are working. The following link shows the same experiment with record/play heads taken from a tape recorder and with handmade cores similar to the ones you've made:

https://www.youtube.com/watch?v=MMD-d-1erk4

Sorry, but I don't know of a way to measure the charges in the core tips. In a way you've demonstrated that current is moving through the windings so the cores are working. And I don't know of a way to test for recorded data on the wire other than playback.

At this point I think the problem is that there's no (or very little) signal being stored on the wire. You might try recording on some audio tape. If you can get that to work you'd confirm that your set up is capable of recording and playback. And perhaps you can find some recording wire to try.

I hope this helps. Please ask again if you have more questions.

A. Norman