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Kevin Weddle
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Posts posted by Kevin Weddle
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I would want to increase the stability of the supply for small signal regulation. Before and in series with Q2 could be a fully biased NPN transistor so that the bias resistors can set the base voltage. Q2 would only need a BE diode to help limit the voltage drop and a VCE zener diode with a voltage best for average use.
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I was thinking of the low current IC's in regard to the high current output. Higher current means a lower beta, a lower impedance and a larger change in current. It wouldn't be an easy circuit to wire up. If any part of the design is wrong or a transistor is damaged or too far out of the design parameters it won't work.
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The power supply draws an enormous amont of current. Voltage regulators have line and load reguation. It's a great 30V supply. Haven't built it yet.
Naw no way. Tell um. -
Opamp U1 is a very good circuit! I think it's absolutely great. Tell us what you think about this!
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My mistake Big Zee, Q3 appears as only a warning that the power supply is shorted. If it were a good power transistor it could reduce the voltage too. The negative power supply should be more than 700mV and a resistor used in series with D9.
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U3 probably doesn't need the negative supply, but adding resistors isn't power saving. Maybe R17 R18 could be changed. But this is an already designed project.
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Hi Big zee. Are you contructing this power supply. Are you almost done!
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I'm looking at R4 in the circuit and it looks like the zener diode D8 at just over 1ma. Is that the feedback ratio of U1? RV1 seems to determine the output voltage. Adusting the offset to produce the desired voltage isn't familiar. Can anyone help explain this?
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Why are zener diodes used in some voltage regulators? Gain dependant on voltage circuitry can deliver any regulated voltage as long as the AC power supply, rectifier, and filter produce the same result. Standard voltage regulators have been use throughout the industry and are in integrated circuit form. Are they more of a universal product used in industry?
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Zener diodes are a current and voltage limited semiconductor. Mostly they are used to improve regulation and are good additions to power supply circuitry.
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It may be some time before todays electonics toys will develope. But they are great and are always fun. We'll see what they can impove on next.
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Question it doesn't look like a bad place to put a power on/off LED. It should turn off rapidly.
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Are there still problems with this general purpose power supply. Give some better designs or a link to better ones.
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Experimental battery chargers are good for the hobbyist, but they fall much short in technological development and will not serve for practical usefulness. Only the correct charger is designed for charging the 8.4v NiCad. But it's fine if you want to power some small circuit.
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About the bandwidth of this filter, you wouldn't be able to use a resonant type. But what about a Sallen and Key filter with a gain of less than 1? A gain of 1 is okay with an input of 20mV, maybe not for 200mV.
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The resistor in this half wave rectified circuit is in series with the capacitor and battery. If you change the resistor to reduce the charging current, the battery could take a week to charge. If the resistor is in series with only the battery, it will charge in a fraction of the time.
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The circuit shows a wall transformer and not a rectified AC power adaptor. So the resistor would need to be in series with the batteries. A half wave rectifier has more ripple, but the 1000uF capacitor with a 1Kohm resistor may charge the batteries slow enough. You probably have a regulated AC power adaptor. So change the resistor to a 2Kohm.
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An analog motor requires an AC signal to change motor rotation direction. Their used more in appliances and their rotation direction doesn't change. Servo motors are normally digital motors. But if it's an analog motor, the frequency output of the DAC and the motors inductive reactance will require more than a power opamp.
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You might try an N channel MOSFET of the same gm and Idss if you think that's the problem. Repairing electronics equipment without replacement parts isn't probably worth it.
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http://www.colorado.edu/physics/phys3330/phys3330_fa05/pdfdocs/AN101FETintro.pdf
This is a good article I came across describing the developments in field effect transistors. A must see for electronics enthusiates interested in physics.
MODERATOR EDIT: Link fixed. -
I have built this supply long ago, it sits in old AT case, but today I found problem, that on negative (-) supply I am having -40V DC against wall plug ground. It's not problem in general, but if you want to supply something that is for example connected to computer through USB it'll blow the fuse if not USB port of computer..
What could be causing this problem?
Serial communications between external devices often have these same sort of grounding problems which are overlooked mainly because the data is transfered reliably. Your better off using an opto-isolator. -
It seems similar to the device asullivan suggested. Microswitches and motor operated cams today reminds me of a Chistmas hobby. Most devices nowdays use bytes. Programmed devices can use bits which is essential to most electrical interfaces.
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You may not want to use a Sallen and Key Butterworth filter unless you want this particluar response, which can be varied. An RC filter has 20db/decade attenuation. A gain dependant on frequency opamp filter circuit can produce 40db/decade ideally. More likely it will have better filtering with added distortion.
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I'll add that the inductor capacitor filter is not acting as a filter, but is dividing voltage. The frequency of the PWM is based on the frequency of the PWM.
0-30V Stabilized Power Supply
in Projects Q/A
Posted
A higher conduction voltage diode has a high impedance, it only shares it with the transistor. Probably around 15V, the impedance drops and the opamp only follows the signal. So there is no small signal regulation. But you can always use an opamp to power low power DC circuits. But almost always they are used in filter circuits. Which isn't good at 1MHz because they are heavy and frequency sensitive and don't function.