## DC relay coil

Started by in sci.electronics.basics7 months ago 5 replies

I have a DC relay with the coil connections marked "+" & "-". Does it matter? The relay operates with either polarity so there is no internal...

I have a DC relay with the coil connections marked "+" & "-". Does it matter? The relay operates with either polarity so there is no internal flyback diode. It's a 24v, 33ma coil for those who want to know. Thanks, Bob

## Step Up Pre Coil/Transformer

Started by in sci.electronics.basics10 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

## Designing The Perfect Coil?

Started by in sci.electronics.basics10 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...

## Inductance calculations

Started by in sci.electronics.basics3 years ago 5 replies

Somewhere there must be a formula for the inductance of a hand-wound coil. Air core, one layer of wire (of given swg) close-wound, diameter of...

Somewhere there must be a formula for the inductance of a hand-wound coil. Air core, one layer of wire (of given swg) close-wound, diameter of former (cardboard, probably inside of toilet paper roll), length of coil,... (what else?), therefore inductance equals ...

## Simple Test for Coil On "Wasted Spark" 2 Cylinder Engine

Started by in sci.electronics.basics4 years ago 26 replies

I suspected a CDI coil wouldn't put out enough voltage for the "energy transfer" -- the worst misnomer ever -- system and suggested shorting out...

I suspected a CDI coil wouldn't put out enough voltage for the "energy transfer" -- the worst misnomer ever -- system and suggested shorting out the spark plug electrode on one of the 2 cylinders by pounding the gap shut or stuffing it with a bit of foil. The theory was instead of jumping two gaps it would only need to jump one. The lower effective resistance would give a better spark on t...

## 6#11oz, 20"

Started by in sci.electronics.basics8 years ago 7 replies

6#11oz, 20", our first great-granddaughter... Olivia Lawless... Father: Chris Lawless Mother: Caitlin Coil Lawless, first daughter of our...

6#11oz, 20", our first great-granddaughter... Olivia Lawless... Father: Chris Lawless Mother: Caitlin Coil Lawless, first daughter of our oldest daughter Madeleine and James Coil (Yuma County Judge). ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | ...

## Automotive relay question

Started by in sci.electronics.basics8 years ago 15 replies

I have a 12V SPST cube relay in my junque box. The diagram molded into the relay?s housing includes a component connected in parallel with the...

I have a 12V SPST cube relay in my junque box. The diagram molded into the relay?s housing includes a component connected in parallel with the coil which looks suspiciously like a resistor. It?s not a back-emf diode: I connected the relay coil using both polarities (using a current-limited power supply) and the same current draw is measured. What is the purpose of this resistor? ...

## Automotive relay question

Started by in sci.electronics.basics8 years ago 2 replies

I have a 12V SPST cube relay in my junque box. The diagram molded into the relay?s housing includes a component connected in parallel with the...

I have a 12V SPST cube relay in my junque box. The diagram molded into the relay?s housing includes a component connected in parallel with the coil which looks suspiciously like a resistor. It?s not a back-emf diode: I connected the relay coil using both polarities (using a current-limited power supply) and the same current draw is measured. What is the purpose of this resistor? ...

## MOSFET switching an inductive, high-frequency load

Started by in sci.electronics.basics8 years ago 8 replies

Guys: I'm an ME working on a project where I must switch voltage to a small coil = on and off at a fairly high frequency (around 25 kHz) with...

Guys: I'm an ME working on a project where I must switch voltage to a small coil = on and off at a fairly high frequency (around 25 kHz) with a MOSFET transis= tor. The DC resistance of the coil is very low (about 1 ohm), but the impe= dance is much higher because of the frequency (about 100 ohms). I'm switch= ing 24 Vdc. Should I specify the max. pulsed current of the transistor based...

## Creating sparks with a mosfet and ignition coil

Started by in sci.electronics.basics8 years ago 29 replies

I would like to generate a series of ~1000 volt sparks continuously, for several hours, using a spare automotive ignition coil I have lying...

I would like to generate a series of ~1000 volt sparks continuously, for several hours, using a spare automotive ignition coil I have lying around. I found this 555 circuit online: http://www.sci-experiments.com/HighVoltagePulser/ My questions: (1) Is a 500-volt MOSFET really necessary? Would a 100-volt IRF530 work alright without frying? (2) Does the 0.1 uF, 250V capacitor take the ...

## How Do They Get So Much Money for Grid Ties?

Started by in sci.electronics.basics9 years ago 2 replies

Are there still some unexpired patents out there? Does a grid tie require a 200 lb copper coil? Bret Cahill

Are there still some unexpired patents out there? Does a grid tie require a 200 lb copper coil? Bret Cahill

## Bifilar inductor?

Started by in sci.electronics.basics4 years ago 27 replies

Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in) https://www.eevblog.com/ (hmm...

Hi all, silly question. Dave's EEVblog was on... there was this bifilar wound coil (starts at ~39 minutes in) https://www.eevblog.com/ (hmm latest video I guess, Mailbag #1049) My question is; how the heck does that do anything inductive? George H.

## Coils

Started by in sci.electronics.basics10 years ago 35 replies

I've wanted to check out some things using big coils - not the sort used for RF circuits, but large coils such as might be found in a Tesla...

I've wanted to check out some things using big coils - not the sort used for RF circuits, but large coils such as might be found in a Tesla coil. I don't have the funds to special order them or to buy them pre-made (assuming they even come that way). I expect I'll have to wind my own... but... How the heck do you do that? What sort of arrangement would work for that? Trying it by ...

## Hey, that's wierd.

Started by in sci.electronics.basics9 years ago 18 replies

I'm seeing something really interesting with the coil I built. I wired up a buck converter circuit yesterday and tried it out, but just with a...

I'm seeing something really interesting with the coil I built. I wired up a buck converter circuit yesterday and tried it out, but just with a switch and resistor tied to the gate of an IRF-1404PbF, which lists a Total Gate Charge of 131nC, which I take to mean nano- coulombs. When the circuit is 'rested', power applied does what is expected. 10uH ...

## What does this circuit do?

Started by in sci.electronics.basics7 years ago 21 replies

If anything. http://reliablehomeenergy.net/wp-content/uploads/2015/03/scheme.png They claim that \$49 for instructions, \$63 for parts get you...

If anything. http://reliablehomeenergy.net/wp-content/uploads/2015/03/scheme.png They claim that \$49 for instructions, \$63 for parts get you a single home "magnetic energy generator" designed by Tesla. http://reliablehomeenergy.net/tl I assume the video has an AC coil under the table.

## Wa-a-ay OT: Overlay to make a cable "coiled"

Started by in sci.electronics.basics10 years ago 13 replies

Back when I was a kid (nearly 3/4 of a century ago :-) there used to be plastic coils that could be applied to a straight cable to "coil" it...

Back when I was a kid (nearly 3/4 of a century ago :-) there used to be plastic coils that could be applied to a straight cable to "coil" it up. Does such a thing exist today? ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-S...

## How to bootstrap

Started by in sci.electronics.basics9 years ago 37 replies

I see the term bootstrapping, used when the designer wants a high impedance and usually low capacitance. I know it involves feedback but that's...

I see the term bootstrapping, used when the designer wants a high impedance and usually low capacitance. I know it involves feedback but that's all I know. I want to learn enough to build a bootstrapped input with 10Meg/2pf impedance. Those are ballpark numbers, the end use would be used to measure voltage on a high Q coil and NOT load it. Frequency 100khz up to 2Mhz, but 10 Mhz adds mor...

## Power in use indicator please ?

Started by in sci.electronics.basics2 years ago 50 replies

I have a water pump in a remote location. Sometimes the pump (120 volts) line springs a leak and then runs all the time with the potential of...

I have a water pump in a remote location. Sometimes the pump (120 volts) line springs a leak and then runs all the time with the potential of burning out pump. I want to build a little circuit that will tell me in my house if it is running. I have in the past build and induction coil out of a transformer and then used an LED to light up when the pump is on. I cut out one of the side

## Inductance Equations using SI Units

Started by in sci.electronics.basics10 years ago 15 replies

I've been planning to wind some coils. I want to get an idea of what sort of inductance I'd get for a given winding, coil diameter and length,...

I've been planning to wind some coils. I want to get an idea of what sort of inductance I'd get for a given winding, coil diameter and length, and so on. These are all air-core, so I don't need to take into account the effects of iron. When I Google for information, I seem to get the same few formulas, none of which are in SI units. I can find equations and formulas that use inches, or ...

## Wireless phone charger

Started by in sci.electronics.basics2 years ago 5 replies

Just for fun I thought I would make a wireless phone charger. I'm not reall= y going to use it but I wanted to build it and just see if it...

Just for fun I thought I would make a wireless phone charger. I'm not reall= y going to use it but I wanted to build it and just see if it actually work= ed. The circuit uses two coils and a 2n222 transistor very simple. Well I can't really get it to work maybe I could get half a volt maybe to p= ast through induction. Then it seems to stop. I connected my meter to the r= eceiving coil to t...