I would like to make a special power supply/converter with a difference. It can be supplied from:
The unit needs to have four outputs, all of which are DC and each of which is configurable internally by a trim pot to deliver four output voltages between 10 and 24 VDC (e.g., 12V, 15V, 18V, and 22V).
I understand that these parameters are often mutually exclusive, but the following considerations are also desirable:
If the overall concept is too big, perhaps someone could direct me to previous power conversion solutions that may be married together to give a solution, and highlight the isolation issues that may apply regarding multiple input connections.
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I've built this passive audio mixer that I really like. The only problem is that anything going through it sounds like it's in a stream of water. Lots of white noise.
After the mixer, it goes into the line level input of an old Teac audio cassette machine. Anything plugged into the cassette machine without going through the little mixer sounds great. The signal to noise is great. Very little white noise is present. What type of pre-amp do I need on each input to et the signal up high enough to override the white noise that my passive mixer generates?
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I built the "Mail Delivered Detector" published in the June ‘06 issue of N&V (http://nutsvolts.texterity.com/nutsvolts/200606/#pg44) and was quite satisfied with the results. However, I found that the device stopped working in the cold weather. Adjusting the 25K pot on the receiver's 567 tone detector restored operation until the temperature changed and the device stopped working again.
As an example, I measured the frequency of the transmitter's 555 timer at 68 degrees F to be 320 Hz, and at 20 degrees F it was 280 Hz.
Can someone suggest any modification which will keep the 555 timer circuit in the transmitter on frequency as temperature varies between minus 10 degrees and 95 F, or a way to broaden the frequency range of the tone detector in the receiver?
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I’ve been a reader for some years, and electronics is my daily work. Now, I have to work with the Motorola PTP 600 radio. The system I am working now has three sets of PTP 600. They were set up the same way at three different locations to communicate to the main control hub. One of the stations has kept the connection pretty well since the first day, but the other two sometimes show slow or very slow data transmit. Looking at the status — as they are all set up with i_DFS — the link capacity sometimes drops to 20, the transmit in teens, and the vector error goes up positive. Please show me how I can get them to work more stably. I am working in the war zone of Afghanistan!
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We would like to operate a single-stroke AC bell that would ring once every time the phone rings in cadence. The telephone line power — 40 to 120 VAC at 15 to 60 Hz — should power the bell. We prefer no external power supply. A typical single-stroke bell has a coil voltage of 24 VAC drawing 0.5 amps. Coil resistance is 10 ohms.
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I’m just getting started with microcontroller cards. What is the difference between an AVR microcontroller card and a PIC microcontroller card? I am interested in purchasing a course kit that includes the books and the microcontroller card for the course.
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Where can I get a schematic for the circuit board in my Stanley model 520 garage door opener? The circuit board has a burnt capacitor and I need to find the value to repair it.
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Conar Model 251 Oscilloscope
I need a schematic or manual for the Conar model 251 oscilloscope which Conar, I understand, was bought out by NRI/National Radio Institute/McGraw Hill. This is an old single channel 10 MHz analog scope. I need the manual to repair the scope. I already know the power supply works and the cathode ray tube works since I see a momentary dot when the scope is turned off. I am on limited income but will be willing to pay for a copy of the schematic or manual for this scope.
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Try this site for your Conar 251 info: www.industrycommunity.com/ee/ee-2-next3/messages/203.html
You might check out www.W7FG.com (Vintage Manuals).
There is an electric pump on our boat that moves diesel fuel from one of four main fuel tanks to a day tank to run the engine. It can sometimes take up to 20 minutes to fill the day tank. Sometimes, we forget the toggle switch is on and the tank overflows through the vent line onto the deck. I need to devise a way to automatically turn off the pump when the tank is full, or at least after a specified interval of 5 to 10 minutes. There is no access for a float switch in the tank. Maybe some sort of timer circuit?
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This problem is easily solved with a "spring timer."
This is a spring driven 120 VAC switch available at Home Depot, Lowe's, or an electrical supply house. Often used to turn lights out in store rooms or laundry rooms automatically when not needed, it is a spring driven electric switch that fits inside a standard electrical box and is available in various maximum times such as one hour or 15 minutes.
To operate, one twists a knob to the amount of time needed, the load comes on, then goes off when the time runs out.
I would like to control the speed of a 3/4 HP 12 VDC motor with a 3.3 VDC microcontroller. I've seen in past issues where PWM was used to control small DC motors but not fractional HP motors.
Can someone show a circuit to interface the high power motor with a low power MCU from a 12V auto battery? Presently, I'm trying to use a Freescale MC9S08QG8 MCU. Ultimately, I would like to use the motor as a brake, and then reverse rotation on a small flywheel for a few revolutions.
The motor goes the same direction all the time, just the flywheel will reverse direction.
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