| |
|
| |
| Feedback |
|
|
Following is a list of unanswered reader questions,
printed in the Tech Forum, from recent issues of Nuts & Volts Magazine.
Be sure to include the ID number printed at the end of the question when
offering a solution. Answers should be e-mailed to forum@nutsvolts.com
November 2008 Issue
Well Pump Alarm
I volunteer my services to our local water department (which is all volunteer except for our Water Operator). We have three well sites whose pumps are located at the well head. These pumps are connected to variable frequency drives within the pump stations. I would like to send alarm signals back from the well heads to the pump station over these wires. Is this possible?
#11086
Howard Epstein
Hacking The Kasey Kinderbot
At the local thrift store, I recently picked up a Kasey Kinderbot educational robot made by Fisher-Price. I thought it might be fun to highjack the controls and run my own programs on the robot. Does anyone know the way to do this? I also picked up one of the Rumble Robots (Bolt Man) and found the schematic at howstuffworks.com but they did not include the bar code pattern for the power cards nor the IR control pattern for the manual controls. Has anyone decoded these yet?
#11087
William J. Black
December 2008 Issue
I recently replaced my SMPS as it was not working. I know the basics about electronics and would like to try to repair it myself (hard disc is not reading). Can someone provide me some information to troubleshoot and repair my unit, if it is possible?
#12083
Karthik
Karnataka
Can I modify a webcam to connect to the RCA connectors on a TV?
#12087
Ken Hilke
New Wilmington, PA
I'm trying to figure out the best (and cheapest) way to control a wing (see diagram) on a race boat. It needs to adjust the wing's angle of attack against the boat's angle of attack given varying speeds. I'm also trying to fit all the mechanicals within the wing itself. Servo speed and accuracy is very important as things can go very wrong very quickly at racing speeds.
#12089
Tom Nusbickel
Santa Ana, CA
I have an inverter with a megatron card that doesn't work. I’ve measured the oscillator voltage and it’s okay. What can I do?
#120810
Juan Garcia
Dominican Republic
I’m looking for a circuit to interface my Pocket PC through the SD slot. I am trying to come up with an interface to use my HP iPAQ for many different applications ranging from data aquisition to robot control.
Also, regarding the data sync cable and power charging, I have a 22.50V solar cell, max output 120 mA. I would like to build a power supply that connects the USB sync cable from the Pocket PC to the solar cell. I'm not looking at using the data lines on the USB, only the power source. What would be the best circuit design to drop the supply voltage down to the normal voltage that the USB port from my desktop PC provides for charging the Pocket PC?
#120811
Richard Forkner
Grand Junction, CO
January 2009 Issue
Is there a simple design guide available for calculating proper capacitor sizes used in the construction of rotary phase converters that use ordinary three-phase motors as the rotary transformer?
#1091
Jack Kleiss
Cloverdale, IN
I need a way to reliably trigger a 555 from a loss of input signal. I've tried several schemes involving capacitor discharge when the input disappears but they have not proven to be reliable.
Keeping the input high apparently doesn't let the device time out, so it needs to be a positive going pulse.
#1095
David Schoepf
Marianna, FL
March 2009 Issue
I am looking for a practical vs. exotic bench setup to determine the gain of some power TO-3 transistors. I'm working with an old piece of equipment that requires matched transistor sets. It was going to be replaced in the near future, but “near” is beginning to look like "someday." So, for the indefinate future, we need to keep the existing units alive and the dead ones restored.
#3093
David Bassett
Summit, NJ
I have designed and built a USB dumb data terminal for Time and Attendance tracking. My problem is that now that the device is in production, static discharge to the device resets the MCU. It's a very simple design using only an LCD, PIC chip, membrane switch (with grounding layer), a plastic enclosure, and a USB cable to connect to the computer. I have a grounding layer on the PCB and the cable's shield and the membrane grounding layer are connected to it. Routing the membrane grounding layer to the cable shield bypassing the PCB ground improves ESD performance, but not completely. What should I be doing?
#3094
Michael Lange
GA
I have an electric bicycle that runs on 36 VDC and would like to make a circuit that would power the lights and radio on the bike. There are four items all powered by various quantities of AAA batteries. There is 1@6V, 1@4.5V, and 2@3V. If someone could provide me with a circuit diagram, I would appreciate it.
#3095
David Luther
Los Angeles, CA
I have purchased an inexpensive DMM which appears to work satisfactorily. Is there a method to measure the input impedance of the meter?
#3096
Doug Poray
Jackson, NJ
April 2009 Issue
On several cable channels, commercials are much louder than normal programming, or the volume level changes annoyingly during a program. Does anyone have a circuit that can be built into a stereo TV to provide an "AGC" function? Ideally, it would be installed by cutting into the low-level L and R audio inputs to the power amp IC (analog signal) and inserting this circuit in-line. Also, it would be great if it could be powered by an available supply in the TV (generally 12V).
#4091
George Nutzul
West Hurley, NY
Does anyone have a solution with a schematic on how to sync a modern inverter like those from Harbor freight — say their 700 watt model — to the grid. (Very important for anyone working with solar and the green problem!)
#4092
Tom Oliver
Dewey, AZ
I need an efficient linear power generator. Any ideas how to make one? Perhaps using a voice coil style or moving magnet in a coil/tube setup. It must be as efficient as possible and able to handle direction and voltage polarity change so that electrical output is maintained at 12 VDC or as close as possible. It needs to work with a push rod with a throw of 3-6 inches.
#4093
Jay Steele
Fort Myers, FL
I want to add a USB port to a CD boombox. How complicated of a process am I looking at?
#4094
Mark
Hawley, PA
Has someone come up with a design for a digital TV converter which can be programmed like a VCR for taping when I'm not around?
Ideally, it would support two lines: one for the VCR and one for the TV. But this isn't a requirement.
#4095
Max Gage
Seattle, WA
I’m trying to build an LED display to show the position of a remote arm. I am using the LM3915 in the dot mode to drive the 10 LEDs. The voltage divider to establish the position of the arm is my problem. I have linked a 10K pot to the arm via a direct link. The arm moves the pot about 90-100 degrees of its travel limits.
This unit is being powered by 12V which is also available for use in the power divider circuit for the input. I have placed in series with the 10K pot another 5K pot as a method to refine the scale of the output. I’ve had no luck setting it up so that when the arm is at one limit, the #1 LED is on and when at the other limit (approx. 95 deg of travel on the pot), the #10 LED is on. I would also like the display LEDs to be adjustable in brightness, as well.
#4096
Charlie Willwerth
Saint Augustine, FL
Is there an up-to-date schematic or project to convert RGB or Composite video signals to VGA (or SVGA, XGA, etc.) and vice versa? I'd like to incorporate this into a few home projects. I don't want to buy one, just build one!
#4097
John Procida
Virginia Beach, VA
May 2009 Issue
I would like to get information on Mylar speakers and their theory of operation. I need to replace a Mylar speaker installed in a Panasonic cordless handset telephone. Can a regular dynamic speaker replace a Mylar?
#5091
James Brendage
Orangevale, CA
I purchased an inexpensive PIR motion detector and did not notice it said "for incandescent only" in small print. It works great with an incandescent lamp, but not well with an inductive load such as a relay or fluorescent lamp. Is it feasible to alter one of these to operate other loads? If so, how?
#5092
Steve Gunsel
Medina, OH
I have five table-top water fountains which I want to run constantly. They are designed to use two AA batteries for each fountain, which is impractical.
1. What plug-in DC power transformer (voltage and amps) can I substitute for the 10 batteries to power all five devices?
2. How should it be wired — in series or parallel?
#5093
Garry Smith
Indianapolis, IN
June 2009 Issue
Can I run a permanent magnet 90 VDC motor on a 1,500W inverter? I need to reverse the motor and was going to run the inverter output through a full wave rectifier. The motor draws about eight amps.
#6091
Bill E.
Warren, OH
Most, if not all, outdoor pedestal lights are 1.5 volts with a very weak LED. With the advent of super bright >10,000 mcd white LEDs, we need a circuit we can drop in (after gutting the old one) that will give a meaningful light source. I entertained a Maxim DC-DC step-up but the existing circuits are current limited. So, how about a 3.x solar source, photocell, a pair of 1.5 VDC batteries, and the charger circuit with photocell switch?
#6092
Ron Spatafora
Plano, TX
Does anyone know of a self-contained, autoranging digital panel meter? There are lots of fixed, 200 mV range, self-contained digital panel meters that simply require a power supply and appropriate voltage divider to measure a fixed range of input voltages. I would like to measure from 1m VDC to 400 VDC with three or four digit accuracy. Or, is there a way to make a self-scaling, autoranging voltage dividing, input circuit that would then utilize a standard self-contained panel meter to accomplish the same task? There are many good quality DMMs that are fully autoranging, but they are very difficult to disassemble and implement into a stand-alone system. Most have auto-power-off circuits and other features that make them too cumbersome to implement.
#6093
Paul
Rocklin, CA
I would like to be able to use an oscilloscope PC application to monitor the 120/240 output of my UPS. I found a couple of applications that utilize the PC's sound input. Can the 240V output be effectively and safely reduced to the voltage level of the PC mike input?
#6094
Curt Timmerman
Big Lake, AL
I’m looking for a circuit to run a low wattage 120 volt incandescent light. The source will be a Parallax BASIC Stamp II microcontroller (5V @ 30 mA per I/O) and the circuit needs to be opti isolated. I’d like to use a triac if possible. The light will be off for short periods of time (two to five seconds) and on for about a minute at a time.
#6095
David Milsop
Humble, TX
I need to build a 24 hour, battery-operated counter with a 2" readout (LED would be okay) that will have the capability to be manually adjusted up/down and reset to 0.
#6096
German Juarez
Santa Ana, CA
July 2009 Issue
Wind Speed Controller
I need a circuit for several applications that need to be switched on/off (open/closed) by relay, depending on wind speed.
The circuit needs to be able to set a minimum wind speed to activate and a maximum wind speed to deactivate. Also, it needs variable activate and deactivate timers (about 30 seconds to five minutes) so that wind gusts will
not activate/deactivate the circuit too rapidly.
There are several stand-alone wind speed devices on the market, as well as included in complete weather stations. They all seem to be wireless in nature and talk to some type of receiver monitor or computer. A stand-alone "wired" wind speed device to controller circuit would be preferred.
#7091
Vonn Hockenberger
Livermore, CA
Inventory Tracking
We have been trying to find a better way to keep track of thousands of inventory items we have on campus. We would like to do this the cheapest and most effective way. Our budget right now is not that large. We have looked at a few applications from iTunes App store, but most of them are web based — "Info already on the web." I was wondering if RFID chips could do this sort of thing? We want to put the serial number, item name, and model number into either a barcode or chip that can be stuck to the item. Is the RFID system able to do this or very inexpensive barcode software? The RFID I am talking about uses those little chips like you find inside a passport.
#7092
Harlan
Springfield, MO
Simple Low Frequency Transmitter
How would I build a low frequency (say 512 Hz), battery operated sine wave transmitter that was small enough to fit inside 1" PVC pipe? I'm not sure if a resistor, capacitor, or crystal is the best; how do you wind a coil antenna to match the frequency?
#7093
Gordon Eden
Naperville, IL
Microcontroller Circuit
I want to build a project using a BASIC Stamp 2p40 to allow me to reset pin setters at the bowling alley I work at from the front desk. I need a way to interface between the BASIC Stamp and the pin setters. The reset button is a 24 VAC circuit and I will be connecting in parallel with the reset switch. I was thinking about using something like an opto-isolator but I want to be able to reset multiple lanes at the same time and am concerned because the Stamp can only sink 60 ma/eight pins, and from what I have seen in opto-isolators, they take 10 ma on the input. This would mean if I reset all lanes at the same time, I would need to sink 80 ma/eight pins. Am I going about this the wrong way or is there a better way to interface between the Stamp and the pin setters?
#7094
Chad Geist
Fargo, ND
Curb Sensor
I would like a circuit to build an electronic automobile curb sensor.
#7095
Lynn White
|
|
|
|
