- #31
Ivan Nikiforov
- 173
- 35
Yes, you're right, the wire is wound in one direction.queenidog said:
Need an electromagnet to play Chess
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The discussion centers on creating a "Phantom" chess game using an electromagnet to move pieces, with players having different polarity magnets. The creator has calibrated their setup but struggles with the electromagnet's strength, finding commercial options inadequate compared to an old solenoid. They plan to build a custom coil using AWG#38 wire but are confused by calculations suggesting low magnetic field strength. Suggestions include using pulsed operation to increase the electromagnet's effectiveness and considering a hybrid approach with permanent magnets. The complexity of the chess game's mechanics, including differentiating player colors and handling special moves, adds to the project's challenges.
- #32
queenidog
- 18
- 5
Well I did answer this question before (maybe it was on the Enginerring forum) but here it is: The chess squares are 40mm across, the players (all custom made by me on a 3D printer) have bases 18mm across so they are 11 mm away from an edge. 2x11= 22 mm, 4mm extra to move the player between the others. The originator posted a video of this action, which is what got me so involved in the first place! Go here:sophiecentaur said:We're still waiting for an answer about knight moves. If the knight can't jump when necessary, other pieces may need to shuffle out of the way. Your software wizard may need to sort that out for you.
- #33
queenidog
- 18
- 5
I have failed. I made another coil, with two layers and a metal core Not being able to determine how much was in each, I just winged it and wound what I thought was the same amount each time. NOT! Coil1 was 358 ohms and coil2 was 1180 ohms, or 149m and 492 m respectively. Total for the two coils in parallel @12V was 362 Gs, @ 24V it was 749Gs. This still pales in comparison to the solenoid (shown in photo on left) which is 1122 Gs @12V, yet is 1/4 the size! If I used a 48 volt supply, yeah that would put my coil higher.
Since I'm nowhere near Edison's 10,000 things that didn't work, I will try again with a different core and try and wind the same amount each time. Since the revs on my lathe are constant, I'll just time everything, say 15 minutes for each coil. I might also use bigger wire, like #36 instead of #38.
If I put a metal can around my coil, like the solenoid, would that help? I'll try that too.
Since I'm nowhere near Edison's 10,000 things that didn't work, I will try again with a different core and try and wind the same amount each time. Since the revs on my lathe are constant, I'll just time everything, say 15 minutes for each coil. I might also use bigger wire, like #36 instead of #38.
If I put a metal can around my coil, like the solenoid, would that help? I'll try that too.
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- #34
Ivan Nikiforov
- 173
- 35
I don't think you've failed. You've almost got the right design. The solenoid on the left has a current of 250mA, and earlier you set the goal to create a solenoid with a current of no more than 130mA. The result you have obtained is very important. Previously, you had 271 Gs, now you have increased this value almost 3 times to 749 Gs. If you made two identical windings, the increase should be 4 times, since the number of turns remained the same 21200, and the current would increase 4 times from 8mA to 32mA. In general, the data obtained needs to be clarified. If the first coil had 1600 ohms, then at 24V the current should have been: 24/1600 = 15mA. The specific resistance of AWG38 is 2.16ohms/m. For 1600ohm, this gives a length of 740m. The following data series is obtained: 1) AWG38 740m 15mA; 2) AWG35 740m 30mA; 3) AWG32 740m 60mA; AWG29 740m 120mA.
- #35
queenidog
- 18
- 5
Thanks Ivan for all your help. It's been informative.
HOWEVER, everyone, I'm changing tactics. After achieving 1738 Gs with an EM taken from a relay and modifying the center rod, I find that this is JUST MARGINAL to move the player effectively. So, as Dave E. recommended once (and I was aware of but thought it too difficult...) I'm going the servo/permanent magnet route.
With a 180 degree servo I can switch in a north magnet or a south magnet. Easy peazy really, as long as I can get the servo in the spot made for the EM, and also that the flipping doesn't catch an edge when the magnet is 5 or 10 degrees from it's destination. The magnets have to come to the same position so that the coding doesn't become horrendous to compensate for two magnets that do not align.
FYI, compare the 1738 Gs EM with these numbers, for various permanent magnets I have: 13x6 mm: 4124, 16x3: 2979, 16x5 (magnets for cabinet doors): 3900, and 10x3: 2380. I tested the latter with my test "sandwich" consisting of 2mm Aluminum, 2.5mm sensor board, and 3 mm acrylic sheet with player on top. works like a CHARM! I chose the smallest magnets for less mass, thus smaller servo, fewer problems swinging up into place. I'll post a photo when I get it working.
HOWEVER, everyone, I'm changing tactics. After achieving 1738 Gs with an EM taken from a relay and modifying the center rod, I find that this is JUST MARGINAL to move the player effectively. So, as Dave E. recommended once (and I was aware of but thought it too difficult...) I'm going the servo/permanent magnet route.
With a 180 degree servo I can switch in a north magnet or a south magnet. Easy peazy really, as long as I can get the servo in the spot made for the EM, and also that the flipping doesn't catch an edge when the magnet is 5 or 10 degrees from it's destination. The magnets have to come to the same position so that the coding doesn't become horrendous to compensate for two magnets that do not align.
FYI, compare the 1738 Gs EM with these numbers, for various permanent magnets I have: 13x6 mm: 4124, 16x3: 2979, 16x5 (magnets for cabinet doors): 3900, and 10x3: 2380. I tested the latter with my test "sandwich" consisting of 2mm Aluminum, 2.5mm sensor board, and 3 mm acrylic sheet with player on top. works like a CHARM! I chose the smallest magnets for less mass, thus smaller servo, fewer problems swinging up into place. I'll post a photo when I get it working.
- #36
berkeman
Admin
- 69,236
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One thing to keep in mind is that the permanent magnets may become a bit demagnetized over time due to the physical movement in and out of other static magnetic fields. I'm not sure how to quantify it, but I think as long as your magnets are ~50% more powerful than they need to be, that the gradual demagnetization over time should not affect the operation of your board mechanism.queenidog said:
https://www.duramag.com/techtalk/magnet-design/causes-demagnetization-permanent-magnets/
- #37
queenidog
- 18
- 5
Wow! I didn't know that. thanks for the info. I have a bunch of the magnets I plan to use though, so they are easily replaceable. I have a Gauss meter to test them
- #38
rbelli1
Gold Member
- 1,090
- 445
It will concentrate the magnetic fields. In your design the opposite pole of the magnetic field is all the way on the other end of the coil. If you put it in a ferromagnetic cup then the opposite poles will be right next to each other. You will probably want to put the chess piece magnets in a cup with the same diameter as the one over the coil to further improve the attraction.queenidog said:
BoB