Re: International standards (2023 Update)

Hi, Thomas. At your apparent level of experise, it might be a better idea just to junk the wall wart and start over. In order to learn something about electronics, you have to start somewhere, and good working basic equipment is part of that.

A variable voltage wall wart isn't really a good idea for a newbie to power breadboards and such because:

• It isn't current limited. If you short it out or place an excessive load on it, you might burn up the wall wart. You could put a fuse on the output, but that might get a little expensive for a newbie.

• It has an unregulated output voltage. That means the voltage will change depending on the load you apply, with greater 120 Hz/100 Hz ripple for greater loads. For instance, a 12VDC 300mA wall wart will show 15VDC or so with no load, and 11.5 or 12.0VDC or so with 300mA load. At full load, you've actually got several volts peak-to-peak of ripple.

If you want to have something you can use for basic breadboarding, you might want to look at a hobbyist kit which will give you a regulated, current-limited DC supply (Look for one based on the LM723 IC). Either that, or get an electronic power supply surplus or on ebay.

Good luck Chris

done that already.

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I'd like to know how you achieved that, in view of my comments highlighted above. Ye canna change the laws o'physics, Cap'n.

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The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
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Radio reset when ESD was applied to certain exposed conductive pins. I would like to monitor the reset pin of the microcontroller using oscilloscope, but worrying that ESD spike might damage the scope which has 250V max rating. Is oscilloscope fast enough to capture ESD spike? What equipments or test setup are needed in order to capture ESD spike? Thanks.

Make sure the pointer has a proper laser drive circuit. Many don't and the one referenced above looks very familiar.

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Clint Sharp

In message , Kim writes

I used to use a mains rated diode an a bypass switch to prolong element and tip life on the Antex irons (BTW, all the sleeve type tips I have seen for Antex irons were iron plated) I have managed to keep the tip of an Antex good enough to work with for so long the barrel corroded and fell apart first!

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Clint Sharp

On 12 Aug 2004 18:26:37 -0700, snipped-for-privacy@yahoo.com (Dummy) wroth:

thin

material

Nickel, copper, and zinc are all compatible with ordinary tin/lead solder. You can solder to any of them. The plating layers are rather thin though. A solder preform or paste along with just enough heat, using hot air or an oven, to get the job done would probably work with either spreader.

Since there are so many variables involved, your answer will probably have to be gotten using empirical methods. Try several samples with different methods and test the "peel strength" of the resulting joints.

Jim

In article , Shmuel Davis wrote: [....]

Imagine a walk across a carpet and touch the box. A spark jumps from my hand to the metal box. Where does it go from there on its way back to the earth?

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kensmith@rahul.net   forging knowledge

I would be worrying about the microcontroller. ESD discharges are very unpredictable and get do much damage to sensitive equipment. There are special test devices to study ESD. Do a Google for ESD test devices and you will see what this involves. Tom

--- YEOWWWW!!! That's just plain scary!

For starters,

1. The MOSFET should be mounted in the channel between the fins on the heat sink, NOT sandwiched between the heatsink and the Veroboard.

1. There's no need to use #10 wire. #16, with a resistance of about 4 milliohms per foot will give you a drop of 50 millivolts per foot with

12 amps flowing through it, which your solenoid will never miss if you keep the wiring SHORT.

1. The clamp diode needs to be mounted on the board with the MOSFET, the whole thing needs to be cut down substantially, and the solenoid needs to be connected to the Veroboard with SHORT wires, whether you use that terminal block or solder it directly to the board.

2. You need to learn how to solder. Tin the wires and the Veroboard before you solder the wires down, and either use a hotter iron or (if the one you have has adequate wattage) hold the one you've got on the joint until the solder flows properly.

1. You should keep the battery, the solenoid, and the Veroboard as close to each other as possible. It's not very important to keep the control circuitry close to the rest of the circuitry, (matter of fact, I think farther would be better than closer) but you should connect an electrolytic cap in parallel with a ceramic cap where the battery leads connect to the board with the control circuitry on it. Also, I'd run the supply leads directly from the battery to the control board instead of letting them pass through the other board in order to eliminate ground loop problems.

--- Why? Instead of solving problems you'll just wind up making more. But, if you want to do it for a learning experience, go for it, by all means!

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-- John Fields

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Well... ;^)

laser drive circuit?

These show the battery, terminal block, protection diode, and the piece of veroboard I've built the mosfet onto. The thin wires from the terminal block will go to the board with the control electronics on.

I was thinking of making a low-quiescent-current regulator using a couple of transistors and a zener diode.

sometimes, yes.

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Not sure that it need be the reset pin being toggled that's doing it. Also not sure that it'll help you any, even if you can catch anything with a storage scope. A non-storage scope would tell you nothing useful.

Sounds like you may have a poorly EMC compliant design. I note that you say 'certain exposed conductive pins' . What are they connected to and why are they exposed when EMC testing ?

It's acceptable IIRC to 'blank off' unused connectors with a protective conducting cover for EMC testing provided that such covers are supplied / installed and the instructions make it clear that they should only be removed when a mating plug is inserted.

You *do* have good chassis ground bonding at all connector shells too I hope ?

Graham

Hi I think the scope would be protected against ESD and that 250V are for constant voltage and not a nSec spike. A scope with 1Ghz BW will allow you to capture a nSec spike. Use "Normal" mode at signal Negedge with threshold set to 1.5V. How do you intend to produce the spike ? Do you have the ESD "gun" ? Amnon

"Dummy" ??? ??????: snipped-for-privacy@posting.google.com...

oh, I thought I had done a neat job of it apart from the messy soldering.

ok. This will make it harder to solder the solenoid cable to the mosfet leads though (less of an end to turn over and solder the cable to)

I know it's a bit heavy - it's just what they had at the shop.

That I don't get - why does it matter to have short wires?

Fairy snuff.

Again, not sure why it matters to have short wires? The solenoid will be about 3 feet above ground level on top of a water tank, which doesn't seem like a good place to mount the box with the electronics. I was thinking of having all the electronics including the mosfet in a plastic box under cover with the battery next to it, the solar panel nearby, and wires running up from this to the solenoid.

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2-4

is

I was thinking that for a high current load, the veroboard traces wouldn't be thick enough to carry it. And the cable is too thick to put through one of the veroboard holes.

OK. I'm surprised it would matter so much.

I'll think about it - thanks.

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No, that wouldn't work.

As shown the RC time constant is long relative to the typical ramp up of the power supply. So pin 2 remains below required 1/3 threshold for a short time, triggering the mono. Then it stays +ve so that it's still high when mono ends, avoiding re-triggering.

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Terry Pinnell
Hobbyist, West Sussex, UK