G
Guest
- Jan 1, 1970
- 0
Audioguru you got me wrong. I was mentioning about Kevin's reply.
Even i know its better to use 78XX.
Even i know its better to use 78XX.
audioguru2
- Apr 6, 2004
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Siddharth,
Thanks for helping Kevin, and your circuit will work here too.
When I unzipped your file, I was surprised that the simple schematic uses more than 1MB of memory.
Thanks for helping Kevin, and your circuit will work here too.
When I unzipped your file, I was surprised that the simple schematic uses more than 1MB of memory.
audioguru2
- Apr 6, 2004
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Ante,
Your experiment inspired me to try it too, and then I continued experimenting:
1) New 9V alcaline battery feeding a 7805 with no load. Current drain = 6mA. Its been going a day-and-a-half now, and its battery measures 7.8V. The regulator feels cold and its output measures 5.05V.
2) I made another one but put a 51 ohm load on it. That's 98mA into the load and the regulator was using only 6mA. The regulator was dissipating 406mW and felt slightly warm. At 4 hours, the battery measured 6.6V, and the regulator output still measured 5.05V.
3) I built a zener circuit with a 1N4733, 5.1V/1W zener, and calculated a series resistor to feed it and feed the load. With a 51 ohm 100mA load, I figured that with a 6.6V battery then a 15 ohm resistor would feed the load 5.1V. With a new 9V alcaline battery, the 15 ohm feed resistor got VERY hot since it was dissipating 1W. The Zener also got hot and was dissipating 816mW. At first, the total drain on the battery was a whopping 260mA. The battery voltage dropped to 6.6V in about 2 hours, when the zener felt cold, and the load voltage measured 4.4V. Lousy regulation.
4) With a new 9V alcaline battery, I tried the zener circuit without a load. Again the drain on the battery measured 260mA, but the zener was smoking a bit since it was dissipating more than 1.3W. The battery voltage measured 6.6V in about 3 hours, when the zener felt warm, and the output voltage measured 5.0V.
So with a new battery and 98-100mA load, the regulator dissipated 406mW, and the zener/feed resistor dissipated 1.8W.
And with a new battery and no load, the regulator dissipated 24mW and the zener/feed resistor dissipated 2.3W.
The zener regulation can be improved by feeding it even more current.
The zener/feed resistor costs more than a 7805 and eats power, so why use a zener? Maybe it's better for low current applications.
Your experiment inspired me to try it too, and then I continued experimenting:
1) New 9V alcaline battery feeding a 7805 with no load. Current drain = 6mA. Its been going a day-and-a-half now, and its battery measures 7.8V. The regulator feels cold and its output measures 5.05V.
2) I made another one but put a 51 ohm load on it. That's 98mA into the load and the regulator was using only 6mA. The regulator was dissipating 406mW and felt slightly warm. At 4 hours, the battery measured 6.6V, and the regulator output still measured 5.05V.
3) I built a zener circuit with a 1N4733, 5.1V/1W zener, and calculated a series resistor to feed it and feed the load. With a 51 ohm 100mA load, I figured that with a 6.6V battery then a 15 ohm resistor would feed the load 5.1V. With a new 9V alcaline battery, the 15 ohm feed resistor got VERY hot since it was dissipating 1W. The Zener also got hot and was dissipating 816mW. At first, the total drain on the battery was a whopping 260mA. The battery voltage dropped to 6.6V in about 2 hours, when the zener felt cold, and the load voltage measured 4.4V. Lousy regulation.
4) With a new 9V alcaline battery, I tried the zener circuit without a load. Again the drain on the battery measured 260mA, but the zener was smoking a bit since it was dissipating more than 1.3W. The battery voltage measured 6.6V in about 3 hours, when the zener felt warm, and the output voltage measured 5.0V.
So with a new battery and 98-100mA load, the regulator dissipated 406mW, and the zener/feed resistor dissipated 1.8W.
And with a new battery and no load, the regulator dissipated 24mW and the zener/feed resistor dissipated 2.3W.
The zener regulation can be improved by feeding it even more current.
The zener/feed resistor costs more than a 7805 and eats power, so why use a zener? Maybe it's better for low current applications.
Kevin Weddle
- Feb 23, 2004
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Siddharth, you know the circuit I am talking about. The zener, because it gets it's voltage from the ouput, will drown out the signal at the emitter. The base still has it's signal. So the signal at the PN junction is really onesided. But if you use a resistor, then the function will still be the same. It's kind of arbitrary, but isn't it interesting. What is the impedance that the signal sees? I bet it's just re because of the constant voltage. But this would make for poor biasing.
audioguru2
- Apr 6, 2004
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Are you talking about the regulator circuit that Siddharth attached in his reply #17? I've seen that circuit many times, it works fairly well. Build one, test and study it.
Kevin Weddle
- Feb 23, 2004
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Thank you for correcting me audioguru. The only difference is that the zener gets it's voltage from the output through a resistor.
audioguru2
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Kevin,
Sorry to correct you again, but the zener gets its current through R3 from the unregulated input on the left, not the regulated output on the right.
Sorry to correct you again, but the zener gets its current through R3 from the unregulated input on the left, not the regulated output on the right.
Kevin Weddle
- Feb 23, 2004
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The circuit I have gets it's zener voltage from the output. It is a commercial power supply.
G
Guest
- Jan 1, 1970
- 0
Kevin it would be nice if you post your circuit here.
Last edited:
Kevin Weddle
- Feb 23, 2004
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From my circuit, which is similar to Siddharths, the input signal is drowned out by a capacitor and the zener gets it's voltage from the ouput through a resistor. Interestingly enough, the voltage of the darlington is high, making the current low. The rated current is 1.5A. I understand the current should be at the midpoint. Also, my circuit doesn't have a pass transistor, it's a regulator.
G
Guest
- Jan 1, 1970
- 0
Kevin its hard to imagine your circuit.Can you put it up?