Voltage dividers
Jun 30, 2006 12:40:20 GMT
Post by xerxes on Jun 30, 2006 12:40:20 GMT
I've been looking at a DAC kit and the diagrams etc. there are some connections on the board that show this:
+5v
+3.3v
0v
I've been looking in my big bumper book of electronics for numpties, which suggests that what I need is a voltage divider circuit.
The input section, the DAC itself and analogue output sections come on one baord and there are separate voltage regulater boards for powering separate sections of the main DAC board. Each voltage regulator board contains 2 separate voltage regulator circuits on a single board. If I use one of the voltage regulator circuits with the output set to 5v, can I do this:
Also, what about the value of the resistors? Would 102 ohm and 200 ohm be better, this would give me an output voltage of 3.3113v, which is closer. How accurate do these things have to be?
I've was reading this article on voltage regulators: www.eleinmec.com/article.asp?16. It seems that you need a transformer with an output a couple of volts higher than the desired output power of the voltage regulator. Could I use a 15VA, 9V+9V transformer using one set of scondaries for the 3.3v output and another for the 5v output?
What the article doesn't explain is what effect the voltage difference between the AC output voltage of the transformer and the desired DC output of the reglator is. For example, if I want a DC voltage of 5v, am I better to choose a transformer with an AC output of 7v, 9v or even 12v? Also how does this effect the temperature and efficiency of the voltage regulator circuit?
Lastly, how do I select the correct VA for the transformer? Presumably underpowered is a disaster and something will go bang. But what about overpowered, presumably something to spare is good, but how much? If I need 1A, should I use a transformer capable of delivering 1.5A, or 5A?
+5v
+3.3v
0v
I've been looking in my big bumper book of electronics for numpties, which suggests that what I need is a voltage divider circuit.
The input section, the DAC itself and analogue output sections come on one baord and there are separate voltage regulater boards for powering separate sections of the main DAC board. Each voltage regulator board contains 2 separate voltage regulator circuits on a single board. If I use one of the voltage regulator circuits with the output set to 5v, can I do this:
Also, what about the value of the resistors? Would 102 ohm and 200 ohm be better, this would give me an output voltage of 3.3113v, which is closer. How accurate do these things have to be?
I've was reading this article on voltage regulators: www.eleinmec.com/article.asp?16. It seems that you need a transformer with an output a couple of volts higher than the desired output power of the voltage regulator. Could I use a 15VA, 9V+9V transformer using one set of scondaries for the 3.3v output and another for the 5v output?
What the article doesn't explain is what effect the voltage difference between the AC output voltage of the transformer and the desired DC output of the reglator is. For example, if I want a DC voltage of 5v, am I better to choose a transformer with an AC output of 7v, 9v or even 12v? Also how does this effect the temperature and efficiency of the voltage regulator circuit?
Lastly, how do I select the correct VA for the transformer? Presumably underpowered is a disaster and something will go bang. But what about overpowered, presumably something to spare is good, but how much? If I need 1A, should I use a transformer capable of delivering 1.5A, or 5A?