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Registered Member #9130
Joined: Sat Dec 29 2012, 03:31PM
Location:
Posts: 17
Hi everyone- I have something I'd like to run by you, to see if you think it might work. I wonder if there is a computer program out there that is able to generate frequencies that I could then run through an amplifier, then into my coil to tune? My uncle suggested that there may be software out there that would allow me to do this.
What do you think? I think it could possibly work.
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
OR you could get yourself a Wavetek model 98 and tune the coil down to 1 Hz resolution if you desire, that's what I do.
Course, you have to factor in the topload and the bottom leadout for grounding, which will throw everything off by 1%. My coil is tuned to within 3%, and it works just fine.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
Most computers cannot output frequencies higher than ~20kHz (since people cannot hear anything above 20kHz), so unless you have a huge coil you probably won't be able to find the resonance.
You might be able to find a sound card with a poorly designed anti-aliasing filter (and amplifier with good high-end bandwidth) which leaks signals out at the full sample rate (up to 96kHz depending on your sound card, which may be enough for a modest size coil), but you are probably better off just using a function generator (or even a 555 timer or 4046 oscillator).
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
You can tune a coil with just a simple 555 timer IC. Just design it for variable frequency and a duty cycle approx. equal to 50% and connect the output (use highest voltage possible - a transistor output stage would help) . Connect directly to your coil via a 10k resistor (or similar) and scope the voltage through the resistor (which will be equivalent to the current). Depending on whether its parallel resonance (i.e. primary tank) or series resonance (secondary coil), you'll be looking for either voltage peak or zero with your scope.
Very simple. No need for anything fancy other than oscilloscope.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Yes, but if you want to know the frequency exactly, you must use a frequency counter (or a fancy scope). But many multimeters can do this and there are quite cheap counter modules on Ebay.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I tried another 'method' last night for measuring the inductance of a coil, using just a signal generator and a DMM, set to 'volts AC'.
I just connected a ~100 ohm resistor to the output of the sig. gen. connected the coil and a 'known' capacitor in parallel, and connected them across the resistor and sig. gen., and then 'swept' until the DMM gave the highest reading, which, in this case, was ~1.5V @ 1225Hz. (the DMM was in parallel with the coil and capacitor)
Obviously, TC coils have different parameters, but the same method could surely be adapted?
(I will be posting more details later in another thread. I did 'scope' it as well, but, if anything, the DMM method was more accurate.)
EDIT: using a digital frequency counter, this method could be adapted to use a 555. No 'scope or sig. gen is required, just a DMM that measures AC volts and frequency.
EDIT EDIT: In fact, I think you could tune two coils without knowing the exact frequency, just using an AC voltmeter and adjustable 555 or similar.
EDIT: There's a fairly simple frequency counter schematic here that looks suitable for TC frequencies. You wouldn't need the 'frequency offset' feature, just connect pin 7 to ground:
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Another tuning method?
