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Ask Technical Questions Here ( research them first, if Google answers it, use Google, Not Us )

You may get an answer, you may not. Please Date Your question. Put the most recent questions at the top of the question list. Put plenty of detail in the question. Your problem may be clear to you, but not so to the rest of us.


Question 6


Date: 2010-01-10

Does anyone have a recommended high voltage AC/DC input DC output regulator? Something for powering MCU devices off the primary mains (115/1/60 US, 200/1/50 EU, ect), that supplies an output voltage of around 3.3V to 7.5V much like a low cost MCU based product might have.

I'm looking for a better design of what might be called an universal off-line regulator. I found this ref, but those 1/2 watt resistors for a 100ma output don't sit well with me.

I also found this linear non-isolated regulator, but I'm not happy with it because it's again wasteful, and it can't offer an isolated output if so desired.

I'm thinking the solution will look something like this, perhaps with a switching frequency around 1kHz, or 10kHz what ever the low FCC limit is.

The general theory in my above sketch is that the high side drive will buck you down to what ever voltage the chip is looking for. Current capabilities would be driven by the high side drive, and bulk caps. Something in the 100ma to 5 amp range would be nice for a broad range of applications.


Question 5


Date: 2009-10-16

Hi. I'm looking to design and build a PLL controlled 33 cm ATV downconverter. The purpose is to have a PLL controlled LO of somewhere around 850 MHz - shifting down from whatever frequency the user selects (via the DIP switches) in the 902-928 MHz band to 60 MHz (TV channel 3). A channel step of 1 MHz is sufficient, but it would be really convenient if the device had enough bandwidth to cover the entire 902-928 MHz span (users with computer tuners would pick 848 MHz to have 902-928 MHz go from 54-80 MHz and would be able to tell their computer tuners exactly where to look. Users using actual TV sets would have to change the LO to alter the tuning since TV sets are not as agile). You can check out my blog for more details.

Where I'm at so far is that it appears that the combination of the MC145151 PLL, SA620 LNA/Mixer/VCO and the MC12080 prescaler together might do exactly what I want. But I'm not really an expert at such things. Is there an easier, cheaper, or easier to get set of components that can work together to achieve the goal?

Is it just as easy as just breadboarding the example circuits from the datasheets? Will breadboarding actually work for UHF RF circuitry?


Question 4


Date: 2009-10-08

Does anyone have a simple circuit for Power over Ethernet (PoE) power supply? I have found a number of ICs that are supposed to help (e.g. MAX5940 .. MAX5943, LTC4257, TPS23750, ...) but most of the example circuits suggest output transformer and optocouplers. That would make my ~$20 design too complex and expensive. Do you know of any cheap and easy way to get 5V or 3.3V from PoE? Thanks!


I really like National's LM5071 chip. Look at the non isolated example circuit on page 17 of the datasheet. It doesn't need a transformer or opto, but you have to be careful as the 5V RTN is NOT common.

Question 3


I am looking for a CEF04N6 transistor for an Acer monitor. China wants to sell me 2 at $10 each plus $50 shipping. The monitor isn't worth more than $100. Please advise. Date: 6/23/08


Aww really? thats just a cheap MOSFET. Go buy something that is 600v 6a rated and drop it in! Any mosfet will work. the pins should be GDS.

Question 2


hello i am looking for a inline and paralel messuring tools ,and was wondering if i can do it with a gyroscoop Date:23-2-2008 more or less


Could you clarify the question a bit? What specifically are you trying to do?

Question 1

how do I add my c code to this wiki?

Feb '08: how do I add my c code so it will be colored in this wiki? I can have it export to a html file and rtf


Currently the fastest way to add c code to the Open Circuits wiki is to copy and paste the plain text, then add a "code" tag before and after the code. Like so:

#include <stdio.h>
int main(void){
    printf( "%s", "Hello, world." );

We can also discuss the main() function.

(hit the "edit" button to see how that is done). Is that what you wanted?

Many IDEs colorize C code; that makes it a little easier to understand. If you want to see those pretty colors, some options we've seen so far:

  • copy-and-paste the source into your favorite IDE. Then it will colorize the code in the way you are used to (which may be different colors than what people with a different favorite IDE see).
  • Perhaps you could try exporting HTML from your IDE (or some other off line colorizer tool or script) and pasting it in. The OpenCircuits wiki accepts some html.
  • Other wiki use a "source" tag that colorizes C code automatically[1]. Should we install that here at Open Circuits?

russ_hensel, --DavidCary 12:51, 20 March 2009 (UTC)

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