Transistor testing

Started by RobH in sci.electronics.basics2 years ago 15 replies

I have some BC547 transistors which I want to use in a circuit, but according to this: Hook the positive lead from the multimeter to the to...

I have some BC547 transistors which I want to use in a circuit, but according to this: Hook the positive lead from the multimeter to the to the EMITTER (E) of the transistor. Hook the negative meter lead to the BASE (B) of the transistor. For an good NPN transistor, you should see ?OL? (Over Limit). If you are testing PNP transistor, the meter should show a voltage drop between 0.


Does a parrot's foot conduct electricity?

Started by Commander Kinsey in sci.electronics.basics2 years ago 73 replies

My pet parrot has a habit of chewing wires but never got a shock. I tested her feet with a multimeter and it was over 20Mohms. My own dry finger...

My pet parrot has a habit of chewing wires but never got a shock. I tested her feet with a multimeter and it was over 20Mohms. My own dry finger is 1Mohm. Are they safe from shocks due to scaly feet?


Problems with 12V and 5V lines on a PC ATX supply

Started by Commander Kinsey in sci.electronics.basics2 years ago 35 replies

Why do (cheap? expensive ones may be better) PC ATX power supplies need current drawn from the 5V line to make the 12V line work correctly? I...

Why do (cheap? expensive ones may be better) PC ATX power supplies need current drawn from the 5V line to make the 12V line work correctly? I have a PC with 3 graphics cards running scientific applications. I acquired three old graphics cards that take about 300W each, and have loads of cheap (CIT) PSUs that are rated at 650W on the 12V line, which is what those cards use. So I run each card ...


Wireless phone charger

Started by Steve Wolf 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...


555 pin3 output

Started by RobH in sci.electronics.basics2 years ago 4 replies

I've been trying out a couple of Automatic Fence Lighting circuits with a 444, 741 and ldr. I posted earlier about the circuits above , and...

I've been trying out a couple of Automatic Fence Lighting circuits with a 444, 741 and ldr. I posted earlier about the circuits above , and the problem I had was that I could not get a buzzer to work from pin3 of the 555. I came across this https://www.electronicshub.org/how-555-timer-ic-testing-circuit-works/ and found that out of x3 555's I had which I thought were faulty, only 1 ...


Schmitt Triggers

Started by RobH in sci.electronics.basics2 years ago 32 replies

I have been looking at schmitt trigger circuits and didn't realise how many variations there are. Anyway I found this...

I have been looking at schmitt trigger circuits and didn't realise how many variations there are. Anyway I found this one: https://reviseomatic.org/help/2-radio/Schmitt%20Trigger%20Light%20Sensor.php The author here says that by adding a 22k resistor to the bottom diagram turns into a schmitt trigger circuit as the top diagram. From other schmitt trigger circuits I have see on yout...


AoE 3rd Ed heavy discount on Amazon UK

Started by Adrian Caspersz in sci.electronics.basics2 years ago 9 replies

A UK heads up, https://www.amazon.co.uk/Art-Electronics-Paul-Horowitz/dp/0521809266 Hardcover, sold direct from Amazon, £23.50 You...

A UK heads up, https://www.amazon.co.uk/Art-Electronics-Paul-Horowitz/dp/0521809266 Hardcover, sold direct from Amazon, £23.50 You Save: £42.49 (64%) I had the first edition at college, and sold it on to a new student. Second edition came out, I was still broke so hunted down an old first on eBay. For me third edition now on the way :) BTW The companion "Learning the Art ...


Measuring Accuracy: 1.0 grade

Started by Bob Engelhardt in sci.electronics.basics2 years ago 3 replies

An Amazon meter is described as having "Measuring Accuracy: 1.0 grade". I found that there is a standard that defines the grades, but is there a...

An Amazon meter is described as having "Measuring Accuracy: 1.0 grade". I found that there is a standard that defines the grades, but is there a simple answer to what "1.0 grade" means in percentage? (I know how difficult it can be to extract simple answers from standards.)


Retro Button Would Further Automation On the Boeing Max & Everything Else That Seems Sophisticated Beyond the Intelligence of Designers

Started by Bret Cahill in sci.electronics.basics2 years ago 51 replies

Put a retro or "my kingdom for a horse" switch on anything that seems unnecessarily over automated or when the additional sophistication is of a...

Put a retro or "my kingdom for a horse" switch on anything that seems unnecessarily over automated or when the additional sophistication is of a minor advantage. If anything doesn't seem perfect, tap the retro switch and you are back to flying by the seat of your pants or at least something that is less complicated / more proven technology. It may seem counter intuitive but this would actual...


Failure mode of LEDs in overcurrent situation

Started by Andrew T. in sci.electronics.basics2 years ago 3 replies

I'm curious about what happens to an LED when it is exposed to a moderate overcurrent situation. This question came about as I was...

I'm curious about what happens to an LED when it is exposed to a moderate overcurrent situation. This question came about as I was troubleshooting some small white LED lights I built using 3 5mm LEDs and a current limiting resistor to run on 12Vdc (supplied by a lead-acid battery charged by solar). After some time, many of these strings would start to flicker or blink. I was about to po...


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