DC relay coil

Started by Bob Engelhardt in sci.electronics.basics11 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


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

Started by Bret Cahill in sci.electronics.basics5 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...


MOSFET switching an inductive, high-frequency load

Started by Don Gilmore in sci.electronics.basics9 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...


How to bootstrap

Started by amdx 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 Steve Wolf 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


Wireless phone charger

Started by Steve Wolf in sci.electronics.basics3 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...


Difference in Coils for Electronic Ignition & Mechanical Ignition

Started by Bret Cahill in sci.electronics.basics10 years ago 6 replies

A wiki article said some of the mechanical distributors could simply be swapped out with electronic ignition distributors. They didn't say if...

A wiki article said some of the mechanical distributors could simply be swapped out with electronic ignition distributors. They didn't say if a new coil was necessary. Bret Cahill


Major Differences In Small Engine Coils

Started by Bret Cahill in sci.electronics.basics10 years ago 7 replies

Maybe the voltages vary somewhat for different point and plug gaps but is it enough to make any difference? . Supposedly Honda no longer...

Maybe the voltages vary somewhat for different point and plug gaps but is it enough to make any difference? . Supposedly Honda no longer makes the coils for their 100 outboard, a 2 cylinder 4 stroke engine. Isn't it likely that other small engines, say from riding lawnmowers, use coils that are pretty much the same? For that matter couldn't a motor vehicle coil work? Bret Cahill ...


MCU reset during relay switches ON

Started by Niresh in sci.electronics.basics2 years ago 7 replies

Hi, Could any please suggest how to avoid MCU reset with voltage glitches/noise during relay switches ON. I have protected the relay coil with...

Hi, Could any please suggest how to avoid MCU reset with voltage glitches/noise during relay switches ON. I have protected the relay coil with free wheeling diode and MCU with 2x10uF parallel with 100nF near VDD of MCU and 1uF across RESET pin. Regards, NiK