Crystal Radio Questions

Started by Joe in sci.electronics.basics8 years ago 10 replies

I'm winding a coil for a crystal radio. The original plan says to wind the antenna coil on top of the tuning coil, whereas another version...

I'm winding a coil for a crystal radio. The original plan says to wind the antenna coil on top of the tuning coil, whereas another version says to wind the antenna coil *adjacent* to the tuning coil, separated by about 1/4 inch. If I wind both versions of the antenna coil on the form, will one winding interfere with the other? That is, I would only hook up one antenna coil at a time, so ...


How to test the primary coil on a microwave oven transformer for a short.

Started by trg-s338 in sci.electronics.basics8 years ago 7 replies

I'm building a spot welder using a modified microwave oven transformer. The project calls for removing the secondary coil windings. In doing...

I'm building a spot welder using a modified microwave oven transformer. The project calls for removing the secondary coil windings. In doing so, I accidentally "bumped" the primary coil with a hammer resulting in 2 or 3 wires in the primary coil becoming slightly displaced by about 1/8 of an inch. I hope someone can tell me how to test the primary coil for a short circuit as a result of t...


How to optimize parameters for making a coil with high-Q?

Started by Arthur C. in sci.electronics.basics9 years ago 22 replies

I want to make a simple coil (inductor) with a Q value as high as possible. Now, I would like to know if there are simple guidelines on how to...

I want to make a simple coil (inductor) with a Q value as high as possible. Now, I would like to know if there are simple guidelines on how to choose the parameters to obtain this. Parameters are: - thickness of the wire - number of rounds - length of the coil - area of cross-section I understand that a realistic description of a coil involves (at least) a parallel parasitic capacitanc...


Coil wrapping ?

Started by mowhoong in sci.electronics.basics10 years ago 2 replies

I had seen a coil wrapped in twin wire. If I design a coil with 1000 T, I use two wire together, so it mean that I only wrapp 500 T, hence it...

I had seen a coil wrapped in twin wire. If I design a coil with 1000 T, I use two wire together, so it mean that I only wrapp 500 T, hence it save my time and work.Dear members do you have any comment ? Thanks Regards


Basic auto ignition electric Q

Started by Paul Conners in sci.electronics.basics8 years ago 31 replies

Single coil, rotor & distributor cap system, 4 cylinder. Is the coil housing grounded? I always thought the coil housing was the return path...

Single coil, rotor & distributor cap system, 4 cylinder. Is the coil housing grounded? I always thought the coil housing was the return path for the secondary circuit / spark current. I know that the primary circuit doesn't use ground in the coil: it is grounded through the ignition points in the distributor (this is a 70's vintage car). Both the original and replacement coils do not...


Step Up Pre Coil/Transformer

Started by Bret Cahill in sci.electronics.basics5 years ago 3 replies

OK Honda no longer makes the original ignition coil that steps up the voltage by 3 -4 orders of magnitude. What's the easiest way to get a...

OK Honda no longer makes the original ignition coil that steps up the voltage by 3 -4 orders of magnitude. What's the easiest way to get a 40,000 volt spark out of a 12 volt ac system with a 100X step up coil? Bret Cahill


Coils

Started by KBSoftware in sci.electronics.basics10 years ago 3 replies

I a bit new to electronics, about 1. Now I'm learning about coils, and have a few questions. I have some coils and I know their Henry...

I a bit new to electronics, about 1. Now I'm learning about coils, and have a few questions. I have some coils and I know their Henry rating, I've found a lot of information on coils. Now I'm wondering if I took a coil let's say a 55uH applied maybe 3v, what would be the voltage resulting. I've seen a coil used in a 3v to 9v dc-dc converter and that's why I'm wondering. I think the coil ...


Measuring variation in inductance

Started by grub...@gmail.com in sci.electronics.basics9 years ago 3 replies

I was wondering what precautions I should take for measuring a coil's inductance. Following some capacitive sensing approaches my idea was to...

I was wondering what precautions I should take for measuring a coil's inductance. Following some capacitive sensing approaches my idea was to use a MCU pin for pulling a pin connected to the coil L1 HIGH and then measuring the voltage drop across a resistor R1 in series to the coil. WRITEPIN+-----------o----UUUU---o--------o---------R1--------| GND \----|


555 timer help

Started by Bob1001 in sci.electronics.basics10 years ago 4 replies

I am new to this newsgroup, I am typically a poster on rec. pyro or metalworking, but I have been working on a new project. I am trying to make...

I am new to this newsgroup, I am typically a poster on rec. pyro or metalworking, but I have been working on a new project. I am trying to make an ignition coil for my new turbing engine, and I am quite terrible at reading electronic designs. I know that I will be needing a 555 timer, and an ignition coil. The input into the coil should be 12 volts. I have built a neef type vibrator switch, ...


Designing The Perfect Coil?

Started by Ron Hubbard in sci.electronics.basics5 years ago 113 replies

I want to do an experiment in brainwave entrainment by making a 7 Hz sine wave oscillator out of an XR2206 frequency generator IC and a LM386...

I want to do an experiment in brainwave entrainment by making a 7 Hz sine wave oscillator out of an XR2206 frequency generator IC and a LM386 amplifier feeding a six inch diameter coil-- which should probably fit around my fat head. ;-) The LM386 has an 8 ohm output, so it shouldn't be hard to find a speaker, if I wanted to use one; but I don't know how to make a good 8 ohm coil to radia...


Measuring science fair motor current ?

Started by ehsjr in sci.electronics.basics9 years ago 4 replies

I helped a friend's 10 year old son build a science fair motor: a coil of wire (20t around a pill bottle former) supported above a magnet by...

I helped a friend's 10 year old son build a science fair motor: a coil of wire (20t around a pill bottle former) supported above a magnet by paper clips with the tops bent into a U. The coil has #14 copper soldered to each end, looks like this: ** ___* *___ * * ** The construction is such that the #14 is rigidly attached to the coil, so it ...


[Q] How to calculate influence of metal object on dc biased coil?

Started by Jason Wilder in sci.electronics.basics7 years ago 10 replies

I have a 100 mm ferrite rod on which I want to wind a coil using 0.3 mm diameter copper wire. The goal is to detect a car passing by at three...

I have a 100 mm ferrite rod on which I want to wind a coil using 0.3 mm diameter copper wire. The goal is to detect a car passing by at three meters. I plan to bias the coil with DC. How do I calculate the number of windings that I have to put on the rod so that I can reliably detect the car? This should be easy I suppose, but I can't find anything about it. Every book will tell you w...


sizing a freewheeling diode for a coil

Started by Matt in sci.electronics.basics10 years ago 38 replies

I am controlling the coil of a relay using a switching transistor. To protect the transistor I intend to use a freewheeling diode in parallel...

I am controlling the coil of a relay using a switching transistor. To protect the transistor I intend to use a freewheeling diode in parallel with the coil. I'm not sure of the issues in specifying the diode. My impulse is to simply use a 1N4007 http://www.fairchildsemi.com/pf/1N/1N4007.html (1000V peak repetitive reverse voltage, 1.0A average rectified forward current) because it is ...


What to use to hold Coil Windings in Place?

Started by Archimedes in sci.electronics.basics9 years ago 3 replies

Hi All Can anyone suggest whats best to use to hold the windings of an Air Coil with about 7 turns, about 12mm long - I know i can...

Hi All Can anyone suggest whats best to use to hold the windings of an Air Coil with about 7 turns, about 12mm long - I know i can use polystyrene cement but are there any other options like maybe candle wax ? Thanks Shelton.


monitor a distributorless ignition system

Started by Mike H in sci.electronics.basics9 years ago 6 replies

I would like to data log commanded spark events for my vehicle. It uses a Distributorless Ignition System which consists of a engine control...

I would like to data log commanded spark events for my vehicle. It uses a Distributorless Ignition System which consists of a engine control computer, a control module, and a coil pack. The coil pack is fed 12v and has control wires. When a control wire is brought to ground by the control module, current can flow through a coil primary winding. The control module holds the ground for a EC...


Vehicle detector

Started by Roger Dewhurst in sci.electronics.basics11 years ago 10 replies

Would a multi turn coil, a metre or two in diameter, buried beneath the surfce of a driveway, with the ends of the coil connected to the input...

Would a multi turn coil, a metre or two in diameter, buried beneath the surfce of a driveway, with the ends of the coil connected to the input pins of a operational amplifier serve as a reliable vehicle detector? R


Re: A question about coil winding

Started by John Fields in sci.electronics.basics8 years ago 3 replies

On Wed, 13 Jan 2010 17:42:23 -0800 (PST), Michael B wrote: > No. > The field strength is related to the number of coils. > So if I start...

On Wed, 13 Jan 2010 17:42:23 -0800 (PST), Michael B wrote: > No. > The field strength is related to the number of coils. > So if I start out and go around the coil form 2,000 > times with one wire, could I get the same effect by > using a multistrand, with each strand insulated > from the adjacent one? --- Well, finally, something that makes sense! :-) Yes. ---


Re: FM Crystal Radio

Started by Mike in sci.electronics.basics10 years ago 1 reply

> > That's exactly the same circuit I was looking at. Uses a small > diameter coil so I can build a set into a plastic project box. How >...

> > That's exactly the same circuit I was looking at. Uses a small > diameter coil so I can build a set into a plastic project box. How > many meters of wire would a need for the coil? I plan on winding it on > a 4 inch long PVC pipe. Well, let's see. 1.5" X Pi X 65 turns = 306" and 306/39.34 = 7.8M. Make it 9M to allow for the taps and lead wires. You'll have to plug in the actual O


Relay Coil Suppression, DC relays

Started by amdx in sci.electronics.basics9 years ago 1 reply

A question often asked is about relay coil transient suppression. I ran across this in my files. It has some good information. ...

A question often asked is about relay coil transient suppression. I ran across this in my files. It has some good information. http://relays.tycoelectronics.com/appnotes/app_pdfs/13c3311.pdf Mike


Inductor calculation?

Started by Winston in sci.electronics.basics7 years ago 22 replies

I am trying to calculate the inductance of a multi-row, multi-layer air-core coil that has a square winding cross section, zero magnetic...

I am trying to calculate the inductance of a multi-row, multi-layer air-core coil that has a square winding cross section, zero magnetic coupling to any other object. Conceptually, it's a Brooks Coil, like you might use in a metal detector. Of the internet and hard copy resources I've used, no two equations produce nearly the same results. I've gotten everything from 219 mH on down...