Let me see if I have this clear:
You want to produce 120-240V at up to 20A but to only turn on the supply when the output is not shorted? You seem to want some form of foldback current limiting.
This will of course have no effect whatsoever on user safety.
High voltage supplies can be dangerous. High current supplies can be dangerous. You are doing both, yet seem unable to grasp basics - like how a multimeter works. Unless you can convince me that what you are doing is sensible and that you are capable of doing it properly then I am unable to help you kill yourself or others nearby.
You want to produce 120-240V at up to 20A but to only turn on the supply when the output is not shorted? You seem to want some form of foldback current limiting.
This will of course have no effect whatsoever on user safety.
High voltage supplies can be dangerous. High current supplies can be dangerous. You are doing both, yet seem unable to grasp basics - like how a multimeter works. Unless you can convince me that what you are doing is sensible and that you are capable of doing it properly then I am unable to help you kill yourself or others nearby.
Yes it is. You missed almost every neccessary steps to make it clear. 1 Describing the problem to be solved (no, a single word, "electrocution" is not enough, because it can happen many ways, most of them can not be avoided by your idea). 2 Drawing a block diagram and giving their names to be able to refer to them. And 3 Telling how do you expect the "invention" to solve the beforementioned problem. Using the previously defined entities.
I'd be willing to consider simple ICs but having to use a phone or full-blown computer to achieve this is not viable. I like to build things as simplistically as possible. I think adding unnecessary cost and complexity takes the fun out of doing things and this is a hobby I do for fun.
Let's not worry about safety so much, ok Debbie? We're all supposed to be men here so let's act like men.
Now what did I say about the way a multimeter works that is incorrect? Does it or does it not measure resistance/impedance? Does it or does it not have protective circuitry built in to prevent an overload from damaging the unit itself?
I think your inability to discern this from what I wrote is your problem, not mine. I'm not inventing anything here. It's a very simple problem for which I asked qualified people to provide ideas on how to accomplish what I want to do. I don't need a step-by-step guide, something as simple as suggesting some circuits to look at or ICs to consider is fine.
My original post outlined a simple logic tree that explained the basic functionality I'm after. That's more than enough for someone who knows what they're talking about to work with, and if it's not, then ask a specific question.
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Here is a restatement of my original post using fewer big words...here we go:
- The Power Supply ALWAYS ON
- Power Supply Leads, aka the part that you connect to a project to give it power, OFF BY DEFAULT
Challenge:
- Power supply leads should become fully energized (aka TURNED ON) when the following conditions are true:
1) The leads are not shorted, as in touching each other.
2) The leads have electrical continuity with a level of resistance > 0 and below a user-definable margin (i.e. 50 ohms) for at least 3 seconds. When this condition is met, the leads become energized (TURNED ON).
3) Breaking continuity immediately reverts leads to the not energized state (TURNED OFF).
It's literally a 3 step program. What part of this is so difficult to understand?
It could just be that none of the people who have responded have any practical EE knowledge to share. If what I was asking cannot be done with passive components, what's the simplest possible way to do it?
Here's what doesn't matter:
- What I am building.
- What it's connected to.
- Why I want to do it this way.
- Voltage or amperage from power supply.
So if you feel any of these things or anything not enumerated in my 3-steps do matter as it pertains to making the circuit I described work, you probably don't have the answer I am looking for. No offense, but I'm not here to chat I want to build...
You said:
"You know if you touch the probes of a multimeter together, it gives you a zero reading and it doesn't try to measure because it "knows" you are touching the probes together. It also can read a range of impedance values.."
It was pointed out to you that this is incorrect.
Really. YOU came here with a problem you want US to solve for you. Most posters here have indicated in various ways that it isn't clear to them what it is exactly you want to accomplish.
So we can do a few things.
a - call it a day and avoid further insults etc and go our own ways;
b - you consider how to more clearly communicate, without insults etc, your problem and someone here helps you solve it.
Your call.
Jan
No, it's not "incorrect". My multimeter can read a range of impedance values and it correctly shows ZERO if the leads are touched together.
If yours does not work this way, it's either chinese junk or broken.
Zero posters have posted a constructive post yet, including and especially you. You do not speak for "us" so don't think that you do. You speak for yourself, and you obviously don't have any ideas to share so why troll?
Getting a little sensitive there with calling my response "insults". What's insulting is that this forum is full of know-nothings who want to chime in and share their worthless opinions, but cannot answer a simple question.
If you don't know, don't talk. If you continue to troll my thread, you will be dealt with as the troll you are. Your call, janice.
It has been stated in plain English twice. If you didn't understand the problem, it leaves 3 choices: ignore thread, ask for clarification, or troll. You chose to troll and you lost. Now run along. Let's keep this place productive. Thanks.
For those who actually do know some basic EE stuff, here is where I'm at:
1) Power supply leads are connected to a relay that defaults to on position. Turning on the power supply causes relay to go to off position, so no power is reaching the leads.
2) The AC mains are tapped with a film capacitor, then connected to a bridge rectifier to deliver a nominal DC voltage at up to 500ma. After the bridge rectifier, a resistor should be added to limit max voltage, then an optional smoothing capacitor may be added to contend with ripple. This is essentially a voltage divider.
3) The +12VDC source is then connected to a relay that defaults to ON, and then that is fed into the test leads. At this point, turning on the power supply results in the leads having a low current +12VDC flowing through them.
4) The magic part. This is where the conditions get tested, and if met, the relay for the +12VDC is set to OFF while the power supply leads are set to ON. This is the part which pertains to my original question.
1) Power supply leads are connected to a relay that defaults to on position. Turning on the power supply causes relay to go to off position, so no power is reaching the leads.
2) The AC mains are tapped with a film capacitor, then connected to a bridge rectifier to deliver a nominal DC voltage at up to 500ma. After the bridge rectifier, a resistor should be added to limit max voltage, then an optional smoothing capacitor may be added to contend with ripple. This is essentially a voltage divider.
3) The +12VDC source is then connected to a relay that defaults to ON, and then that is fed into the test leads. At this point, turning on the power supply results in the leads having a low current +12VDC flowing through them.
4) The magic part. This is where the conditions get tested, and if met, the relay for the +12VDC is set to OFF while the power supply leads are set to ON. This is the part which pertains to my original question.
SsZERO said:
If these two quotes correctly describe your level of understanding electronic circuits, you should not be designing any 'protective' circuitry, or even any circuitry involving mains voltages. With your low level of understanding and your complete overestimation of your capabilities, you represent a risk to yourself and possibly to others.
Unless we believe in fairies, a multimeter does not magically know you are touching the probes together and shows zero instead. Your multimeter measures all the time, and because it is not designed to read low impedances correctly, it displays 0.00 when you touch the probes together.
If it was more precise, it would probably read some 0.xx ohms as most multimeters will do when touching the probes together.
Unless you really have superconducting leads or a really expensive 4-wire-measurement meter, it should be reading a few hundred milliohms instead of zero - otherwise it is chinese junk or broken.
Have a nice day,
Rundmaus
Darwin-award competitor.
Somebody plugs in 2 wires to a power source while touching them. (Stupid already.) Sees no harm. Thinks it is safe to touch them. Connects a sink to the source. Sink doesnt have insulation. Grabs 2 surfaces connected to high voltage. Dies.
I know how to make the described circuit. Should I help?
Somebody plugs in 2 wires to a power source while touching them. (Stupid already.) Sees no harm. Thinks it is safe to touch them. Connects a sink to the source. Sink doesnt have insulation. Grabs 2 surfaces connected to high voltage. Dies.
I know how to make the described circuit. Should I help?
I would strongly recommend the mods to close this thread, as live mains circuitry without an isolation transformer is discussed. Thread has been reported.
Rundmaus
I am a wimp, so I worry about safety. I quite enjoy living; I realise that real men like you like to be electrocuted daily just to show how tough they are. I can't remember whether crass sexist insults are specifically prohibited in the forum rules but they are certainly not a good way to gain cooperation and wise advice from decent educated folk.SsZERO said:
You are trolling your own thread. I guess that is useful practice for someone aiming for a Darwin award.
SsZERO - please read and follow the Forum Rules.- Status
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