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MP
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Posts posted by MP
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If you are looking for simple....
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Nice pdf file, Billy. Looks just like mine on a smaller scale. You might want to add a bit of a warning in your article about heat. The best etch is done with the highest heat of the etchant, with one exception. Above a certain temperature, the etchant chemicals become airborne. Eveything in the room with exposed metal will become rusted and you will be breathing unhealthy fumes. I am pretty sure this temperature is 105 deg. F but you might want to verify the exact temp before adding to the article. I have seen articles printed about this before, but I do not recall ever seeing a warning about the high temperature danger.
MP -
If you want 220 instead of 110, you can use a voltage doubler circuit after the transformer to achieve this. This is just diodes and capacitors. Mixos has posted a diagram somewhere on this site with a schematic for voltage multipliers.
...or just use a different transformer that will give you the 220. This is all based on the ratio of turns between primary and secondary.
MP -
I actually have two data sheets on this device. One from BayLinear and the other from National. The National Data Sheet is dated May 2003. Both data sheets list the same specs. 3.5 mA as Typical minimum load current "Min". The BayLinear Data Sheet lists the Minimum load current" Max" as 5 mA., whereas the National gives this a 5 mA spec for the LM117 and 10 mA for the LM317.
I doubt that there is any difference in the BayLinear and National chips and National is probably just playing it safe. Oddly enough, the Minimum load current "MIN" is what really makes a difference, so it is pretty much a mute point. If it is a real problem for you, just go to baylinear's website and buy their LM317.
http://www.baysemi.com/LM317%20Data%20Sheet%20REV%2009142002.pdf
They also send samples, so if you would like to compare theirs with the National, you can do so without risk of cost.
MP -
Thanks John.
That should get me started. I appreciate the help.
MP -
I think that would be a question for Jan, the author of the Transformer information in the Articles section of this site. I believe he has made the offer to help in another post somewhere on this forum. You can send him a message in this forum.
MP -
http://www.electronics-lab.com/articles/transformers/index.html
MP -
I have exhausted my sources for a cross on the above mentioned transistors. Any help would be appreciated....or if anyone knows the specs, I can find something similar from this information.
Again, any help would be much appreciated.
MP -
First, I will have to assume you are talking about a power supply with AC output, since such a filter will do nothing with DC.
Secondly, the frequency and phase of the circuit really are not relative to the voltage since they are related to the timing and lag of the signal whereas the voltage is the amplitude. Any passive filtering will take away from the amplitude somewhat, but this is simply loss in the circuit and not a characteristic of the LC configuration.
But, perhaps I have misunderstood what you are asking.
MP -
Yes, the feedback resistor determines the current. A little about this can also be found in the LM317 data sheet.
I am glad to hear that all is well.
MP -
It is a little more complicated than that and the cure is dependent upon the characteristics of your circuit.
It is a well discussed topic and I am not an expert on it. Using the search words, "compensate negative impedance", I find 83 pages of articles on google.com . Many are pdf files with schematics. I would start there.
MP -
I do not have a ready made circuit for you. I would have to design it and I do not have the time to jump into another project at the moment. When I have the time available, I will put something together and upload it to the forum.
MP -
OUS was meaning Outside the US.
Did you find anything out from those sources? I have not had a chance to pursue it since my last post.
MP -
glebka11:
Receive the wave with an antenna into a vari-loopstick, then rectify the signal with a diode and a few filtering components. You will not get much current, but I am sure it would light a bulb or LED if you tune it well enough.
MP -
Actually, if you use a "black Light" bulb, it will take less time and not generate the heat requiring a fan. The heat actually impedes the imaging process with the photo etch chemicals. My system uses 4 18" tubes and can produce a 12" x 12" board in a very short period of time.
If you only need a small light box, you can find the round bulb and use that. It will cut down your time, lessen the fire hazard, and give better photographic results.
Hope this tip is helpful.
MP -
Yes, up to the allowable value of the resistance. (V/R=I)
After that you get heat and after that you get the smoke if the resistor cannot handle the power dissipation. ;D
MP -
Yes, these are for high frequency filtering. It is hard to find a 0.6 microfarad or 0.7 microfarad capacitor, which is what this makes up. Also, some designers like to parallel capacitors because each capacitor charges to the same voltage, without regard to the behavior of the other capacitor. Personally, I have never built a circuit that was critical enough to require this.
MP -
What kind of accuracy are you looking for? Thermisters are not that bad for most applications. You might also look at the LM34 and LM35 from National Semiconductor.
Again, you need to list how tight the spec. And how are you calibrating it? Another question: are you using a microprocessor to read it? The ADC resolution will also need to be high enough for the high accuracy.
MP -
I have built quite a few of these. There is a LM317 calculator in the "Articles" section of this site. On the page, there is a link to a tutorial with some added information. In addition, if you could post your schematic including the information written on the back of your wall wart, I am sure we can figure it out.
One thing to check for now: which wire is + and which is - from the wall wart. They are not always Center +.
MP -
Yeah, I think Radio shack discontinued the 555 some time ago, too. They haven't caught on that it still exists, either.
MP -
You are losing a bit when you pass the DC voltage through the rectifier bridge. The rectifier bridge is for the AC input. Just tie into the circuit after the 4 diodes that make up the rectifier bridge or somewhere on the trace that goes to the input pin of the LM317. As long as you have enough current to begin with, your problems should be solved.
MP -
Beerman,
Eagle 4.11 has a free hobbyist version. I highly recommend it.
http://www.cadsoftusa.com/freeware.htm
MP -
I am not aware that anyone has discontinued this device. Where did you get that information?
You can get the Texas Instruments SN7407 for about 60 cents at digikey. I just checked their website and they had more than 500 in stock.
MP -
I have purchased these in the past. The legs are bent to an angle which permits them to snap into the circuit board for a snug fit. I have not seen any sockets for them, but perhaps they do exist.
MP
Big Datasheet Database!
in Electronic Resources
Posted
Wow! Nice Find.
MP