The Hobby Corner
Updated on:  Friday, December 18, 2015 08:20 AM

 

  The Hobby Corner:
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- 100+ Construction Project Ideas

 The Design Corner
 
The Hobby Corner
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Capacitance Proximity Switch Technology      --      Commercial Capacitance Proximity Switch  (Faraday Switches)


      100+ Construction Project Ideas  

"Below are over 100 construction project ideas I have been collecting for many years. Some I have actually built, others never made it beyond the conceptual stage and would therefore require some experimentation to finalize a design. All would require some additional work in the areas of documentation and packaging. Let me know if any of these seem like the kind of kits that you would be interested in. I would also like to hear some of your ideas."       Dave Johnson, P.E.

OPTICAL COMMUNICATIONS
AND ELECTRO OPTICS

Long range optical through-the-air voice audio transceiver, Half duplex operation (push to talk). Powered off 6 AA batteries (9v). Single IR LED source. Camera tripod mounted. Two 4" fresnel lens optics (one for transmitter and one for receiver) with a range of over 1 mile, larger lenses could extend range to 5 miles. Accessory kits could be added later to modify same unit to send computer data at 56K baud over long distances and maybe up to 1M baud over shorter distances. (I have lots of circuits, just needs some refining and packaging work)

Long range optical remote controller, Simple on/off operation, either click on/click off or momentary, relay contact output. Something like a TV remote controller but much longer range, perhaps up to 1000 feet. Options might include different relays for AC or DC switching, mechanical or solid state contacts. Might be used to turn on and off porch lights open garage doors or operate industrial controls. (I have circuits, needs some work)

Long range target shooting with light beams, A variation on the above theme. Would use a plastic toy rifle equipped with a pulsed IR source (might be simple triggered spark gap or xenon flash). Multiple targets would flash a light when hit with the pulsed IR light. Range might be as far as a thousand feet. Another concept might allow the device to be mounted onto existing rifles for long range target shooting without ammunition. Perhaps like the Army, one could shoot blanks and use the muzzle flash. (I'd have to think about this one)

Through-beam or reflective intrusion alarm, Pulsed IR LED transmitter and a matching receiver in separate boxes. Would detect anyone breaking the beam with boxes pointing at each other. Could also be used in a reflective mode where IR light bounced off object triggers the alarm. Could be used as an entrance annunciator for stores, doors, driveways etc. Improved circuitry allows for battery operation and longer ranges. Transmitter can operate for years on one 9v battery. Small lenses could increase the range to perhaps 500 feet in through-beam mode, reflective mode might have a range of 100 feet. (I have all kinds of circuits, only needs packaging work)

Wildlife camera triggering device, A variation on the above theme but designed for video or photographic camera system. Would activate shutter or turn on video camera for period of time. Unit would be ideal for automatic electronic cameras. Mechanical camera would require some kind of solenoid to trigger the shutter. System could also activate remote flash. (Some mechanical work would be needed to finish the design) Maybe used for bird feeders to alert people that a bird is nearby.

Optical Fiber Remote DVM probe, Modify good quality DVM with fiber optic transmitter. Remoter receiver detects encoded light signals and mirrors the DMV's display. Remote readout could be 1000 feet from DVM. Idea takes advantage of the features of the DVM but allows the user to monitor the measurements from some remote location.

Optical Fiber Remote Scope Probe, A more complex variation on the above concept. Would send high frequency signals (up to 100KHz) to a scope. The optical fiber method allows complete isolation and much longer distances between the test point and the oscilloscope. (Concept only)

Sunshine U.V. monitor, Powered off 9v battery for days. Would display the relative intensity of the U.V. portion of sunlight. Could help sunbathers know when to turn over.

Might use a glass filter that passes U.V. but blocks visible light. The U.V would shine onto a plastic sheet that fluoresces visible orange light. The visible light would be detected by a PIN detector. Maybe use sheets that route the light to an edge for increased efficiency. (Concept only)

Single PV cell battery charger, Size cell picked for battery size. Uses some of the latest DC-DC converter ICs that can operate from a single 0.5v solar cell. Turned off during night. In theory, the circuit could charge nearly any kind of rechargeable battery from just one PV cell. (Designs exist)

Optical Fiber sun power meter, Device gives remote readout of relative intensity of sun. Great for conducting solar energy surveys. More complex circuit could collect long term solar energy readings in Watt-hrs per square meter. (concept only)

Telephone flasher, Unlike the one sold by Radio Shack this unit would be battery powered. It would trigger a xenon flash each time the phone rings. Unit begins charging the lamp's storage capacitor after the first ring, thereby keeping the standby power to a minimum. Should get about 20,000 flashes (rings) from two C cells. (Concept design only)

Optical Strobe Tachometer, Another great use for xenon flash tubes. Would use flashlight reflector with short gap (0.5" or less) xenon flash tube. Ideally, the circuit would be battery powered. Flash rate dial from 1 flash per second (60RPM) to 200/sec (12,000 RPM). Perhaps several scales for an accurate setting. Flash duration would need to be less than 20us, flash energy would have to drop at high pulse rates to prevent flash tube distruction. Commercially made devices cost several hundred dollars. (I have only some basic circuit concepts worked out)

Fluorescent lamp strobe light, Yes, you can get lots of cool white light from standard 40 watt fluorescent tubes. Cathode ends are kept warm with small line powered transformers. Large emitting area of lamps give softer shadows on the disco dance floor but still can stop the action. Maybe up to 10 flashes per second at about 6 watt-sec energy (160v and 500uF cap). Figure flash duration would be less than 100us, then we should get about 6,000 watts of light per flash. (Would require more experiments to finalize a design).

Baseball fastball speed monitor, Might use a square frame the size of the standard strike zone. The battery powered system would optically measure the time for the ball to pass through the frame. Pulse width generated would be inversely proportional to ball speed. Would give a digital readout of the speed in MPH. Might use existing ambient light.

Bullet velocity monitor, Variation on the above theme. Tripod mounted, picture frame shaped system positioned some distance in front of the gun. Would measure the time for bullet to pass two narrowly focused measurement zones. Might use low power IR laser. Would give a digital readout of velocity in feet per second. (Just an idea) Say 12" between frames. At 1000 feet per second a bullet would take 1ms to pass through.

Long range distance measuring device, System would use nitrogen sparks as a light source. Flashlight reflector collimates the emitted light. Would measure the round trip for the launched light pulse to be returned. Light travels at about one foot in 1ns. An object 100ft away would cause a delay of 200ns. Spark could be generated by piezoelectric crystals.

Snow/rain monitor, Works by monitoring the optical back-scatter reflections off of the raindrops and snowflakes. (concept only)

Special IR fluorescent lamps for night vision illumination, High efficiency IR lamps can be made to order in standard sizes. Much more efficient than tungsten incandescent lamps with IR filters in wide area illumination applications. (Have info on lamp mfgr and special phosphor supplier)

Traffic counter, Counts cars passing a point on a street. No cables across street. Simple optical device placed low to the ground detects passing car. Battery operated, LCD counter. Might also be mounted high up on a light, telephone or power pole. Could be rather small in size. (concept only)

Traffic Speed Monitor, Using two vehicle sensors such as above, the speed of a vehicle could be measured. Might be used by neighborhoods to monitor cars going too fast. Might be linked to a small digital camera to take photos of the speeding car.

Plastic optical fiber linked sensors, Micropowered sensors send data to master fiber optic receiver. Distances over 300 ft would be possible with cheap plastic cables. Could measure weather info, such as temperature, pressure, humidity, wind speed/direction etc. Other industrial monitoring would also be possible. (concept only)

Custom Optical Fiber Sensors, Measures, temperature, magnetic fields, electric fields, vibration, speed, displacement,

Optical through-the-air linked remote sensors, Same idea as above but would send the data over short or even very long ranges. Could get 40 mile range in clear air conditions.

Multi-channel optical remote control system, Similar to radio controls for model airplane but uses special encoded light pulses. Depending on the type of light source, the range could be a few hundred feet to several miles. Might even use pulse position encoding, so only two pulses would need to be sent for 256 different commands.

Super large corner cube light reflector, Uses common mirror tiles. Great for retro-reflective experiments. May be used for measuring distance using very short IR pulses. Might be able to build a plywood panel that would hold a large number of reflectors.

Spark gap light pulse generator, Tiny sparks in open air have a broad spectrum. Some companies have light pulse generators using nitrogen (air) sparks that last less than 10ns and can generate over 100,000 watts of light. Such short durations are useful for optical distance measuring techniques. I experimented with some piezoelectric flame ignitors to generate some nice bright light pulses. (concept only)

Optical Fiber Light Burst Generator, An optical fiber bundle of different lengths turns a single light flash into multiple flashes. The position of the light flashes in time could send a unique code.

Optical Cordless microphone, Uses an optical technique. Good for fixed positions like churches, podiums, microphones on stands and maybe camcorders. Sends the audio from the fixed position to a receiver. No FCC license needed. (concept only)

Xenon flash triggered on/off controller, A battery powered flash transmitter sends a light pulse to a matching light receiver. The receiver contains a solid state relay that can turn on and off a load up to 600 watts. The unit would normally rely on reflections off walls, floors and ceilings however with an added lens on the receiver and transmitter, the control signal could have a range of 20 miles. (Concept only)

Optical signal sniffer, Broadband circuit converts modulated visible and IR signals to be monitored on an oscilloscope.

Wide area cordless stereo headset, Improved circuitry allows for longer ranges, wider areas of coverage and better audio. Up to 500 feet range instead of the usual 75 feet with most units. (concept only) Would use an array of IR LEDs or small fluorescent lamp. Maybe even xenon flash lamp. Both channels transmitted from one light source.

Optical RS-232 Computer Link, Uses fluorescent lamp to send information over a wide area. Great for offices, schools etc. No cables or FCC license.

Optical Through the Air Remote Intercom, Sends audio over to barn, cottage, storehouse. Uses optical through-the-air techniques. Range to several miles. Line powered or perhaps use rechargeable battery, recharged by solar cells. Remember, No FCC requirement. Half duplex push-to-talk operation. Special transmitted tone could turn on a noise maker on the unit.

Cordless Telephone system using optical through-the-air transmission,

Uses a base station attached to the phone line and a second portable unit positioned some distance away. Great for linking a house to a tennis court or pool that may be too far away for standard unlicensed RF or one that needs to be a secure link (Cannot be listened into like RF links).

Video signal transmitter using through-the-air optics, Uses a FM technique to keep the signal quality high. Laser diode light source. Might be used to like small camera to a TV monitor.

Underwater Optical Communications, Using optics? Maybe OK for short distances. Would get lots of scattering due to particles but that may be OK for a swimming pool.

Optical DTMF transceiver, Use it for control systems.

Wide area optical music broadcasting system, Uses modulated fluorescent lamps.

Fiber optic phone, Single optical fiber sends and receives voice audio.

Underwater xenon flasher for lakes, ponds, unusual effects. Turns itself off during daylight hours.

Driveway annunciator, Optically through-the-air linked to base unit. No wires

Long range telemetry from weather station, Use light flashes to send the data.

Large area light broadcaster, Used for hearing-impaired in churches, schools and even movie theaters. Bathes area with modulated IR light. Signal picked up by small box warn around neck or attached to pocket. Drives headphones, 9v battery powers the unit.

Audio head phones without wires, Circuit sends audio signals to headphone using modulated light. Technique might be used to audio on airplanes.

High LED current pulses from inductive fly-back technique, Inductive fly-back technique used to pulse LEDs with high current. A high inductance primary in excited with current from some low voltage power supply. When current is turned off, the collapsing magnetic field generates a higher voltage across the coil that when routed to a LED can drive it with a high current pulse. Might be able to get 10 amps of peak current into the LED to produce very bright flashes of visible or infrared light.

SENSORS AND TEST CIRCUITS

Go/no-go transistor tester, Tests NPN and PNP transistors. Very simple circuit. Audio tone indicates if transistor is OK, NPN/PNP selector switch but no on/off switch, only draws power when testing a device. Great for sorting unmarked devices. Can even measure most transistors still wired in a circuit. (I still have the unit I built 25 years ago, works fine)

1 amp current injector, Unit injects 1 amp of current through unknown resistance. Standard DVMs can then measure the resistance by measuring the voltage drop. 0.0001 ohms can easily be measured. Power source is two "C" cells. Already published in Nov. 1992 Popular Electronics.

Safe transformer tester, Circuit would use very low 60Hz voltage source. You would use a DVM to measure AC to determine turns ratios. Supplied charts would help figure out the color codes used and determine the transformer VA rating based on core measurements. (concept only)

Barometric pressure monitor, Circuit uses surplus absolute pressure transducer. Output can be scaled for mm of mercury, inches of mercury or even newtons per square meter. Great for remote weather stations. Could also be used as an altimeter. (concept only)

Sun intensity monitor, (Solar insolation) Simple circuit displays the available solar power in watts per square meter (Typically 1000) or watts per square foot (Typically 100). Output could be sent to a computer data collection system to record long term solar energy surveys. (concept only)

Humidity Monitor, Uses inexpensive capacitance type sensor. LCD readout. (concept only)

Wind power meter, System would use a standard 4 cup anemometer. Its output would connect to a circuit that would display wind speed and actual wind power in watts per square meter. Great for conducting wind energy surveys. The circuit uses a microprocessor that takes the raw speed data and computes the wind power. It could also integrate the power over time and give a readout of energy in watt-hrs per square meter. This could also be done using analog ICs but would be more difficult. (concept only)

Seismic geophone signal amplifier, Surplus geophone is buried in the ground. It can detect footsteps, car movements, animals and earthquakes. Can be made into very sensitive detector for wide area property protection or intrusion alarm. Lots of such detectors are available in oil equipment surplus outlets. (This idea too may have been published some years back but would still be interesting.)

Capacitance water level sensor, Uses two copper areas on circuit board to measure the level of water inside a tank. (concept only)

Remote household power/energy monitor, Connects safely to breaker box. Remote LCD readout of KW and total energy use in KW-hrs. Perhaps send inductive pulses through the wall, so no holes would have to be made in house. Ideally, the display would be mounted next to a house thermostat.

Earth ground signal amplifier, Looks at very low frequency (10Hz) signals between two probes stuck in the earth. Circuit might detect foot steps or car traffic.

Sound Exposure Monitor, Measures long term exposure to loud sounds.

Dust accumulation monitor, Used to alert maids in motels when it is time to dust. Must be cheap and low power.

Pond Depth and Position Recording System, Plots water depth and position of boat on pond.

Static electricity monitor, Helpful in assembly stations, can locate sources of high static fields.

Universal Thermocouple temperature probe accessory for DVMs, Designed to display temperature in C or F. Maybe show how temperature probes can be made. Unlike other silicon based probes, thermocouples can measure temperatures to 4000 F.

DC current probe, Probe clips onto the wire carrying the current. Uses an off the shelf Hall effect device.

Electromagnetic field monitor, Simple monitor connected to DVM used to measure the level of fields around electronic devices. Some people believe that long exposure to the fields can cause health problems.

Isolated lawn moisture monitor, Measures moisture but keeps monitor isolated from signal transmitter. Optical technique.

Lawn moisture monitor for sprinkler system, Uses a special sensor whose capacitance changes with moisture. Sensor buried in ground. Circuit would link to a sprinkler system and inhibit watering of the lawn if it does not need the extra water.

Inhalation detector. Monitors breaths. Could be used to control oxygen delivery system.

Oxygen concentration monitor. Uses ultrasound, velocity of sound changes.

Bicycle grade monitor, Displays the steepness of hills. Might also work for trucks.

Live power line wire sniffer, When held near live 120vac wires the device emits a tone and lights a light. Great electrician's aid. Can help isolate active wires. Commercial devices do exist, but are expensive. With a sensitivity adjustment, could detect wires behind walls. (Concept only)

Very Low RPM Converter, Accurate frequency readout, down to 0.1rpm. Perhaps a microprocessor could keep track of the time between rotations and produce a digital readout.

Rowboat strokes per minute display, Sensor on the oar would feed a signal to a microprocessor circuit with a LCD display. The battery powered circuit would then display the strokes per minute. Might be good for training purposes.

SECURITY AND ALARM SYSTEMS

Doorknob alarm, Uses classic touch capacitance technique. (I know how to do it but have not worked out all the details) To be useful the system would have to draw low current but emit a very loud noise when triggered. It would need to operate for at least 100 hours (12 8 hour nights) before changing the battery. Assuming 4 AA cells, the current drain would have to be less than 10mA. Without a dedicated earth ground reference the capacitance change sensitivity would have to be high.

Static field disturbance monitor/alarm, Very interesting concept. Great for the experimenter looking for something different. An area I have been experimenting with for over 15 years. Uses earth's natural electric potentials. Simple circuit indicates body motion around unit. Powered off a 9v battery. Can detect human motion 50 feet away. Some suggested experiments can make circuit directionally sensitive. (I have lots of data and some working prototypes).

Earthquake alarm, Simple system would be set off when certain kinds of motion are detected. Perhaps a strong magnet, suspended by a spring, with sets of coils nearby would work. It would have to work for about one year from a 9v battery. (I'd have to think about this one)

Power failure alarm, Activates an alarm and turns on a battery powered light whenever the circuit fails to see 120vac power.

Computer theft alarm, Sounds alarm when computer is moved, connected inside computer. Or, perhaps attached externally to one of the port connections.

Capacitance proximity alarm, Measures the capacitance between unit and surroundings. Human stepping on plate increases capacitance. Requires large surface area and earth ground reference. Detection plates could be mounted below wood floor. No visible sign of detection from above. Maybe two plates could be used and the capacitance coupling between the two plates monitored. A full length mirror might also work to detect humans walking passed.

Farm leakage current monitor/alarm, Detects hazardous leakage from old power lines. Would sound an alarm when severe leakage occurs. Would need a 60Hz inductive pickup coil.

Theft photographic camera, Might modify a cheap automatic film camera, triggered by theft detection circuit. May have to be battery powered.

Human motion triggered electronic still camera system, Might modify a standard video camera and a computer system to capture still images of humans in specific zones in the camera=s view.

Picture frame human motion detection and alarm, Passive infrared detector hidden in picture frame. Might be used to turn on lights, sound a noise generator or an alarm.

Warning barricade sign flasher, Flasher for road warning signs and barricades. Turned off at night. Maybe charge the battery during the day with small solar panel. Xenon flash might be more efficient. Might also look at highly efficient yellow LEDs. It would need to be as bright as existing flashers but last longer and maybe cheaper.

Water flowing in pipe alarm, Water to sprinkler, washer, dishwasher, etc. Sounds an alarm if flow takes place when device is not turned on.

AUDIO AND VIDEO SYSTEMS AND CIRCUITS

Solid state Theremin, Musical instrument played with hands above two metal plates. One plate controls the frequency, the other the volume. The device was at one time used to make bizarre sounds for old science fiction movies. Old designs used vacuum tubes, high voltage and RF. New design could be safe and simple to build. (Concept only).

Ultrasonic sniffing microphone, Unit shifts ultrasound frequencies to lower frequencies. Lots of birds, bats, insects, and mechanical parts emit ultrasound. Kit could include ultrasonic dog whistle to calibrate and test unit. (I think I've seen such circuits in some old magazines, still might be an interesting project).

Infrasonic microphone, Unit picks up very low, subaudible sound. The sound frequency is then shifted higher so humans can hear the sound.

Electronic stethoscope, Key to the project is the construction of special electret microphone. Maybe it would use a small modified suction cup.

Bird or wildlife TV camera, Tiny color TV camera is mounted near an animal feeding station such as a bird feeder. Maybe battery powered. Connected to a radio transmitter. Video from camera is received on unused TV channel. People could get closeup videos of favorite birds or animals feeding. Unit would have to have a solar panel to keep the batteries charged. Might automatically turn off the camera during the night. Perhaps some kind of remote on/off switch so the camera was only turned on when desired. A direct cable connection to the TV display would be awkward.

CD quality stereo headset transmitter/receiver, System has improved signal processing technique to increase range and audio quality.

Two wire, multi-station intercom, Hands-free answering of a call.

Automatic activation of audio power amp when signal present, Would turn on the power amp when music is playing.

COMMUNICATIONS SYSTEMS

Electrostatic transmitter/receiver, Based on electric field disturbance research. Device could send audio through walls and floors over some distance to remote receiver without RF. (Concept only)

Induction coupled transceiver, Sends information through walls of homes using magnetic pulses. Might be good for outside thermometer, power meter, water meter, computer data, audio. No holes to drill through walls. Range would only be 6 feet or less.

Wide area computer network, Full duplex system links multiple computers within an office. (concept only)

CONTROL SYSTEMS

Low power voice triggered relay (VOX) Adjustable sensitivity. Dynamic microphone. Dynamic mic would draw lower power. Maybe 3v to 9v battery powered. 600 ohm output, not amplified. Would go directly into mic 4 pin push-to-talk jack of CB or ham radio.

NASA motor controller, Uses NASA's concept of controlling the power factor of induction motors to increase efficiency. Can save about 30% energy on refrigerators, dryers and air conditioners. Circuit would need nice current vs voltage phase monitor. Some motors using capacitors for starting will require the control circuit to use some special start-up circuit.

AC/DC 120vdc motor speed controller, Uses SCR and bridge rectifier. A DC voltage controls the firing phase angle of the SCR with respect to the zero cross point. Maybe a 0v to 5v DC voltage from a microprocessor could control the phase angle to produce a 0% and 100% motor power. Maybe generate a 120Hz signal from the line voltage that is fed to the microprocessor. Use an optically isolated technique to send the SCR trigger pulses from the micro. If load is put before the bridge rectifier, it would receive AC. If it was wired into the circuit after the rectifier, the load would receive DC.

Room lighting controller, Keeps lights on if unit detects motion. Turns off light with no motion after say 2 minutes

Dog whistle remote switch, Battery powered unit is activate using an ultrasonic dog whistle. Maybe use a quality dynamic microphone with a series resonant LC circuit, tuned to the ultrasound frequency.

POWER SUPPLY AND ELECTRICAL CIRCUITS

Exploding wire pulse generator, Use some 110 Amp SCRs to build a capacitor discharge system that can vaporize small gauge (30ga) wires with a very loud bang. I built a 350v 20,000uf (1200 joule) discharge system several years ago that really packed a punch. Besides blowing up wires, the capacitors can be discharged though a big copper coil. The magnetic fields created can throw objects and crush aluminum cans. Safety features would of course have to be built into such a system.

Small fluorescent lamp night light, Single 1 watt lamp produces as much light as 4 watt night light. Lasts very long time. Perhaps 2 1 watt lamps would be used.

Small fluorescent lamp replacement for 25w bulb, Great for outdoor lighting, garage door lights, etc.

Fluorescent lamp dimmer, Designed for 2 to 6 40 watt lamps. Ideal for kitchens, etc. (concept only)

Solid state fluorescent lamp ballast, Uses multi-turns ratio transformer technique to minimize power factor problems. 120vac line powered.

12v to 120vac inverter, New design concept allows a smaller unit to produce up to 250 watts of clean sinewave power. Old systems could only produce about 1 watt per cubic inch. New design can yield about 10 watts per cubic inch, maybe more. (concept only)

Darkness triggered light, Circuit turns on light only at nighttime. Classic circuit but still might be interesting to build.

Occupancy controlled light circuit, Keeps lights turned on if circuit senses human presence. Such a system could save a lot of electricity for some offices.

DC powered piezo-electric fan, Fan needs 130vac at 60Hz. 0.1 watts. The fan does not move a lot of air, but what air it does move it does so with high efficiency. Perhaps a circuit could be used to efficiently boost the drive voltage so a low voltage DC supply could be used. Would need some kind of DC/DC converter circuit with an "H" bridge. Could this concept be scaled up to produce much larger fans?

Rechargeable super capacitor energy storage system, 10 farad super capacitor is kept changed by a small solar cell array. Supplies enough energy for several dark days. Might be used for flashing lights or some other very low power devices.

CONSUMER PRODUCTS

Barking dog stopper, Powerful ultrasound pulse is triggered by a dog's bark. (concept only)

Electronic scarecrow, System would detect the motion of any animals within a radius of about 20 feet. Detector would trigger a powerful burst of audio white noise to scare them away. I tried this and it works. (Would need some packaging work)

Emergency light flasher, Looks like normal wall mounted toggle light switch but when the switch handle is placed in the middle "flash" position, the light flashes on and off. It could be used to alert neighbors of a problem, or just to help someone find your house. (I have the circuit design, it only needs some packaging effort)

High voltage bug zapper, Maybe battery powered, maybe solar powered. Maybe capacitor discharge type. Black light to attract bugs.

Lie Detector, Designed for parents to get children to confess. Only needs to give parents some idea of truth.

Home EKG with personal computer display and monitoring

Hook patient up with probes, monitors heart during sleep.

MISC PROJECTS

Make your own power electrets, Describes how the mix and bake some special waxes to produce cup cake size electrets.

Sound proof room plans, Shows how to modify a room to be nearly sound proof. Great for loud music listening room.

RF shielded room plans, Illustrates how to build a room for minimum RF emission to the outside world.

 

 

 
 
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