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MP
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Posts posted by MP
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ante, I am not sure what you refer to the zapco circuit?
If you refer to the darlington pairs in the inverter project, the emitters are not directly connected to ground on the first transistor.
This is only a problem when you have parallel transistors sharing a common ground on the emitter.
MP -
A great book for this and connecting all kinds of other devices to your computer is "Controlling the World with your PC" by Bergman. It gives you examples of circuits as well as the programs to write in Basic, C and Turbo Pascal. If you can find this book, I am sure you will not be disappointed.
MP -
The question was how to find the current of the secondary. Unless some things have really changed since I was in school, you look for impedance on a transformer to calculate current. Impedance is the ratio of voltage to current. Z = E / I. This is the beginning. From there you go with the other formulas to find other parameters. Remember, the transformer was designed using formulas. Therefore, formulas will tell you what you need to know from a few characteristic measurements on the device.
BTW- Never connect an unknown transformer to mains to find out what it will do.
MP -
No. I see no gain here and a question as to whether the circuit will function as originally intended with the voltage divider network that it will create. This is not the same as the resistors in the darlington configuration from the article. Note how you will be adding voltage dividers in combination with the other resistors already in the circuit.
MP -
marsman, I have done what you are talking about, but I have not run the wires to such length. You will not have cross talk, but you will require more current than what you needed before. How many watts is this power supply rated? If it is an older computer with a small power supply (230 to 300W), you could purchase a newer PSU on the internet for around US$15 in the 400Watt category. You can figure the resistance of your wire by the gauge. I have a chart somewhere and I will look for it. At the worst, you might have to increase the size of the wire, making a special cable.
A lot will also depend upon how many devices are powered. Floppy drive, CD, hard drive, etc. To streamline, get rid of anything that is not necessary. This will lighten the load.
MP -
Wow! You have been busy.
I think the 1000KB attachment size limit is good since many have slow connections. It would slow down traffic on the site for larger uploads/downloads.
MP -
tuzvihar,
That comment is still in debate. The person who made the comment has not built the project. Those who have already built this project have not given me a reason to believe there is a problem with it as yet.
Welcome to the forum. I am glad to see someone who is actually building a project instead of redesigning it in their head. Please keep us posted on how it performs for you.
MP -
We need as many power inverters as contributors want to post to this site. There is no limit set for posting schematics.
It is also important that when you are going to challenge a design, that you build the circuit, find the faults and then post your findings. Otherwise you only cause more confusion.
Please note that I have locked this topic. This thread is not useful to the building of a project.
Experience shows that this type of commenting or ridicule does not help anyone.
MP -
The darlington article would seem this way if you only looked at the schematic and read the first few lines. If you read the article close enough you will learn that these resistors are not necessary and that they can be added to speed up the transition. Not to keep the supply from floating. This is the reason ON Semi uses this method. Speed of transition.
I gave some thought to posting a schematic with both versions with and without the resistors, but elected to post the complete article and let everyone read instead.
MP -
BTW, I think you are misinformed about darlington pairs. I have attached a pdf document with information regarding them. Darlington pairs are in nearly every IC on the market.
MP -
looks like the collectors are tied together to me. What schematic are you looking at? Perhaps I am on the wrong page.
MP -
eliminator, how are you with microprocessor chips? If you are familiar with them, then you might want to consider sending the information to the chip first, format the data in some way, then feed the data to the serial port of the PC instead. You will need other hardware to interface the parallel port to all of the different types of signals that you want. Some will be voltage levels and some will be pulses.
MP -
steven, since you have already built this circuit, could you please reply to the questions asked?
MP -
That was probably confusing... my last post was in response to reply# 21. I should have used the quote.
MP -
siddharth, the statement in the previous post is not true. You need at least 6.5 volts to get a steady 5 volts out of a 7805, but there is no "low cut off voltage" where they will not work. You have a loss. If you supply 3 volts, you will get something like 2.5 volts on the output. This application is not common for a 5 volt regulator, but it will work. Also, since it is not a common voltage from the regulator output, you will not want to calculate your voltage divider for 5 volts.
MP -
When did this become a forum where someone gets kicked around because they post a schematic which is a useful tool to them? You should applaud him for sharing. If you have helpful comments, that would be different. If you want to make fun of someone go to a different forum to do so.
Hopefully, he will be willing to share his other tools, be it an octal latch tester or whatever.
There are a lot of hobbyists out there who remove the parts they use from "electronic junk". The down side of this is to know the parts still work before using them. Knowledge should not have a price and this is a way to keep the knowledge free.
If you would like to share a better design for doing so, then please post it.
MP -
The correct way to use a zener for voltage regulation is to pass the voltage through a resistor first, then to the zener. This is learned in first year basic DC electronics. Of course the zener got hot.
MP -
pmontone, the output of your power supply would connect also to the input of this project. Then you will have a digital display.
There is a conversation about this project that will also give you pointers. You should use the search to find it or follow the link from the project.
MP -
Good job steven. Many on this list do not understand the salvage thing.
MP -
audioguru, in your comments to hotwaterwizard you mentioned that he should change the 2 diodes in the first transistor stage to resistors in his design. These transistors are connected as a darlinton pair. Adding such a resistor would disrupt the whole purpose of using a darlington pair. It sounds as if you are changing the design to an audio power amplifier.
MP -
No, I have not heard from Staigen for some time.
Staigen, are you still dropping in?
MP -
siddharth, you are correct. Once you know the light and dark resistances of the LDR, you can look at it like it is a simple resistor and use the voltage divider formula. The reason I like to use PNP transistors in such an application is because they are turned ON when the base is at ground potential.
MP -
The hobbyist does not have the luxury of knowing that 14,999 units are working so it must be a component failure and not a mistake in the board layout, design, or something else. The hobbyist also will put a lot more time into a circuit that would never be considered in a manufacturing situation. For a manufacturing company, it is a fast piece of cash. For a hobbyist, it is a work of art. Where the manufacturing industry would never use such a testing device or use a part that was removed from somethng else, a hobbyist would have a use for such a testing device. This community holds an International audience. Perhaps you have the luxury of Radio Shack or similar. There are places in this world where even an op amp is not so easy to come by.
By the way, siddharth, your method does not test the op amp under any loading, which is where you would normally see the failure.
MP -
Ante, this subject was started by mixos and I think he and staigen have a list of changes that they have made. You might contact him direct. He has been very busy with keeping up the site.
MP
Convert 0-30V 3A PSU to 5A or more
in Electronic Projects Design/Ideas
Posted
ginji, thank you for the update on your progress. Good work!
MP