Have you tried your woven coil? Been thinking of making one here but they just seem too hard to shield
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Just finished my MMP and found it a pretty straight forward build. Instructions are easy to follow and the quality of the board from Silverdog is good. Its only an experimental board so I am not going to put it all in a case but I think it would definitely benefit from sheilding. In my workshop there is lots of RF interference from fluros, lots of SMPS and various other instruments so there was quite a bit of noise on most of the test points. I am also using an unsheilded, 345uH relatively high capacitance coil and running the board from a 12v 10A power supply which doesnt help. Even so, I am pretty impressed with the air tests. With a small 3mm bolt I get about 10cm.
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Originally posted by CAS View PostJust finished my MMP and found it a pretty straight forward build. Instructions are easy to follow and the quality of the board from Silverdog is good. Its only an experimental board so I am not going to put it all in a case but I think it would definitely benefit from sheilding. In my workshop there is lots of RF interference from fluros, lots of SMPS and various other instruments so there was quite a bit of noise on most of the test points. I am also using an unsheilded, 345uH relatively high capacitance coil and running the board from a 12v 10A power supply which doesnt help. Even so, I am pretty impressed with the air tests. With a small 3mm bolt I get about 10cm.
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Originally posted by josewashere View PostHave you tried your woven coil? Been thinking of making one here but they just seem too hard to shield
The idea of a "spider basket" coil is to wind the hot end of a coil inside, and wind around and around towards the cold end and in effect the hot end becomes encapsulated in increasingly "colder" windings. That way the static-prone end becomes shielded in the very coil it is made of. Of course, I have no idea if it really works, and I made mine free-style, which means it is ugly-ish. It will serve its testing purpose.
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I just ordered a PCB. Here's my BasketWeave Coil. It measures 320uh and 1.5 ohms.
I'm hopeing it shields itself via the outer windings. I just drilled alternating holes approx.
the size of 6 or 8 wires. If you look close I had to add an extra row as the wires take
more space when wound. I don't have a working PI to try it on yet but soon.
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@Qiaozhi, I may suggest a small improvement for a future release of the board. I placed a MUR460 diode in series with R3 resistor (my choice, not a suggestion), but it turned a bit of a struggle, as the diode's pins are very thick. I had to grind one pin so that it may enter a hole. Having larger holes there could be beneficial, as R3 has thick-ish pins as well.
I also have a suggestion to clarify a small detail regarding a damping procedure. Resistor R12 (1k) is in parallel with the damping resistor R1 if monocoil is used, and it is a part of a negative feedback circuit of an op amp. Therefore, when adjusting a damping resistor, one must have U5 (NE5532) running, or otherwise R12 is not going to show its 1k resistance at small amplitudes. Perhaps it would be a good idea to split this resistor in two 510ohm in series to avoid arcing, or at least give it a bit more room, as most obviously many will go for higher voltages and faster coils, and this resistor will be forced to take the most damping load on itself.
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Originally posted by Davor View PostResistor R12 (1k) is in parallel with the damping resistor R1 if monocoil is used, and it is a part of a negative feedback circuit of an op amp. Therefore, when adjusting a damping resistor, one must have U5 (NE5532) running, or otherwise R12 is not going to show its 1k resistance at small amplitudes.
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Originally posted by Silver Dollar View PostI just ordered a PCB. Here's my BasketWeave Coil. It measures 320uh and 1.5 ohms.
I'm hopeing it shields itself via the outer windings. I just drilled alternating holes approx.
the size of 6 or 8 wires. If you look close I had to add an extra row as the wires take
more space when wound. I don't have a working PI to try it on yet but soon.
[ATTACH]30887[/ATTACH]
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GB circuit works!
GB circuit works! I made it on a protoboard together with a 555 generator to mimic real world timing, and I only skipped trimmers to avoid clutter - fixed values are OK for the proof-of-concept. Anyway, the timing works as it should. The next step is to place the components onto a perfboard and hook it to its proper places.
The attached files are as follows:- the corrected schematic using simple NAND CD4011 instead of a slightly unpredictable CD4093, and taking control over Schmitt trigger by means of simple resistors
- CRO photo of a same thing in jpg format - obviously working as advertised
- same thing, only as a zipped LTspice folder
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