Portable Muscular Bio-Stimulator

This is a small, portable set, designed for those aiming at look improvement. The Bio-Stimulator provides muscles' stimulation and invigoration but, mainly, it could be an aid in removing cellulite. Tape the electrodes to the skin at both ends of the chosen muscle and rotate P1 knob slowly until a light itch sensation is perceived. Each session should last about 30 - 40 minutes.


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Portable Muscular Bio-Stimulator

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C1 generates 150µSec. pulses at about 80Hz frequency. Q1 acts as a buffer and Q2 inverts the polarity of the pulses and drives the Transformer. The amplitude of the output pulses is set by P1 and approximately displayed by the brightness of LED D1. D2 protects Q2 against high voltage peaks generated by T1 inductance during switching.
Parts :

• P1-----4K7 Linear Potentiometer
• R1-----180K   1/4W Resistor
• R2-----1K8  1/4W Resistor (see Notes)
• R3-----2K2  1/4W Resistor
• R4-----100R   1/4W Resistor
• C1-----100nF  63V Polyester Capacitor
• C2-----100µF  25V Electrolytic Capacitor
• D1-----LED  Red 5mm.
• D2-----1N4007  1000V 1A Diode
• Q1,Q2-----BC327  45V 800mA PNP Transistors
• IC1-----7555 or TS555CN CMos Timer IC
• T1-----220V Primary, 12V Secondary 1.2VA Mains transformer (see Notes)
• SW1-----SPST Switch (Ganged with P1)
• B1-----3V Battery (two 1.5V AA or AAA cells in series etc.)

Notes :

• T1 is a small mains transformer 220 to 12V @ 100 or 150mA. It must be reverse connected i.e. the 12V secondary winding across Q2 Collector and negative ground, and the 220V primary winding to output electrodes.
• Output voltage is about 60V positive and 150V negative but output current is so small that there is no electric-shock danger.
• In any case P1 should be operated by the "patient", starting with the knob fully counter-clockwise, then rotating it slowly clockwise until the LED starts to illuminate. Stop rotating the knob when a light itch sensation is perceived.
  Best knob position is usually near the center of its range.
• In some cases a greater pulse duration can be more effective in cellulite treatment. Try changing R2 to 5K6 or 10K maximum: stronger pulses will be easily perceived and the LED will shine more brightly.
• Electrodes can be obtained by small metal plates connected to the output of the circuit via usual electric wire and can be taped to the skin. In some cases, moistening them with little water has proven useful.
• SW1 should be ganged to P1 to avoid abrupt voltage peaks on the "patient's" body at switch-on, but a stand alone SPST switch will work quite well, provided you remember to set P1 knob fully counter-clockwise at switch-on.
• Current drawing of this circuit is about 1mA @ 3V DC.
• Some commercial sets have four, six or eight output electrodes. To obtain this you can retain the part of the circuit comprising IC1, R1, R2, C1, C2, SW1 and B1. Other parts in the diagram (i.e. P1, R3, R4, D1, D2, Q2 & T1) can be doubled, trebled or quadrupled. Added potentiometers and R3 series resistors must be wired in parallel and all connected across Emitter of Q1 and positive supply.
• Commercial sets have frequently a built-in 30 minutes timer. For this purpose you can use the Timed Beeper the Bedside Lamp Timer or the Jogging Timer circuits available on this Website, adjusting the timing components to suit your needs.

Disclaimer: we can't claim or prove any therapeutic effectiveness for this device.

Whistling Kettle

 

Most electric kettles do not produce a whistle and just switch off when they have boiled. Fitting a box of electronics directly onto an electric kettle (or even inside!) to detect when the kettle has boiled is obviously out of the question. The circuit shown here detects when the kettle switches off, which virtually all kettles do when the water has boiled. In this way, the electronics can be housed in a separate box so that no modification is required to the kettle. The box is prefer-ably a type incorporating a mains plug and socket. In this application, the current flowing in coil L1 provides a magnetic field that actuates reed switch S1. Since the current drawn by the kettle element is relatively large (typically 6 to 8 amps), the coil may consist of a few turns of wire around the reed switch. The reed switch is so fast it will actually follow the AC current flow through L1 and produce a 100-Hz buzz. The switching circuit driven by the reed switch must, therefore, disregard these short periods when the contacts open, and respond only when they remain open for a relatively long period when the kettle has switched off.

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Whistling Kettle

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The circuit is based on a simple voltage controlled oscillator formed around T2 and T3. Its operation is best understood by considering the circuit with junction R4/R5 at 0 V and C4 discharged. T2 will receive base current through R5 and turn on, causing T3 to turn on as well. The falling collector voltage of T3 is transmitted to the base of T2 by C4 causing this transistor to conduct harder. Since the action is regenerative, both transistors will turn on quickly and con-duct heavily. C4 will therefore charge quickly through T2’s base-emitter junction and T3. Once the voltage across C4 exceeds about 8.5 V (leaving less than 0.5 V across T2’s b-e junction), T2 will begin to turn off. This action is also regenerative so that soon both transistors are switched off and the collector volt-age of T3 rises rapidly to +9 V. With C4 still charged to 8.5 V, the base of T2 will rise to about 17.5 V holding T2 (and thus T3) off. C4 will now discharge relatively slowly via R5 until T2 again begins to conduct whereupon the cycle will repeat. The voltage at the collector of T3 will therefore be a series of short negative going pulses whose basic frequency will depend on the value of C4 and R5. The pulses will be reproduced in the piezo sounder as a tone.
The oscillation frequency of the regenerative circuit is heavily dependent on the voltage at junction R4/R5. As this voltage increases, the frequency will fall until a point is reached when the oscillation stops altogether. With this in mind, the operation of the circuit around T1 can be considered. In the standby condition, when the kettle is off, S1 will be open so that C1 and C2 will be discharged and T1 will remain off so that the circuit will draw no current. When the kettle is switched on, S1 is closed, causing C1 and C2 to be discharged and T1 will remain off. C3 will remain discharged so that T2 and T3 will be off and only a small current will be drawn by R1. Although S1 will open periodically (at 100 Hz), the time constant of R1/C1 is such that C1 will have essentially no voltage on it as the S1 contacts continue to close.
When the kettle switches off, S1 will be permanently open and C1/C2 will begin to charge via R1, causing T1 to switch on. C3 will then begin to charge via R4 and the falling voltage at junction R4/R5 will cause T2/T3 to start oscillating with a rising frequency. However, once T1 has switched off, C3 will no longer be charged via R4 and will begin to discharge via R3 and R5 causing the voltage at R4/R5 to rise again. The result is a falling frequency until the oscillator switches off, returning the circuit to its original condition. As well as reducing the current drawn by the circuit to zero, this mimics the action of a conventional whistling kettle, where the frequency rises as more steam is produced and then falls when it is taken off the boil.
The circuit is powered directly by the mains using a ‘lossless’ capacitive mains dropper, C6, and zener a diode, D2, to provide a nominal 8 V dc supply for the circuit.  A 1-inch reed switch used in the prototype required about 9 turns of wire to operate with a 2-kW kettle element. Larger switches or lower current may require more turns. In general, the more turns you can fit on the reed switch, the better, but do remember that the wire has to be thick enough to carry the current. It is strongly recommended to test the circuit using a 9-volt battery instead of the mains-derived supply voltage shown in the circuit diagram. A magnet may be used to operate S1 and so simulate the switching of the kettle.
Warning. This circuit is connected directly to the 230-V mains and none of the components must be touched when the circuit is in use. The circuit must be housed in an approved ABS case and carry the earth connection to the load as indicated. Connections and solder joints to components with a voltage greater than 200 volts across them (ac or dc) must have an insulating clearance of least 6 mm. An X2 class capacitor must be used in position C6.

Simple Steam Whistle

This circuit consists of six square wave oscillators. Square waves are made up of a large number of harmonics. If six square waves with different frequencies are added together, the result will be a signal with a very large number of frequencies. When you listen to the result you’ll find that it is very similar to a steam whistle. The circuit should be useful in modelling or even in a sound studio.

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Simple Steam Whistle

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This circuit uses only two ICs. The first IC, a 40106, contains six Schmitt triggers, which are all configured as oscillators. Different frequencies are generated by the use of different feedback resistors. The output signals from the Schmitt triggers are mixed via resistors. The resulting signal is amplified by IC2, an LM386. This IC can deliver about 1 W of audio power, which should be sufficient for most applications. If you leave out R13 and all components after P1, the output can then be connected to a more powerful amplifier. In this way a truly deafening steam whistle can be created. The ‘frequency’ of the signal can be adjusted with P2, and P1 controls the volume.

Lighting Up Model Aircraft

This circuit provides aircraft modellers with extremely realistic beacon and marker lights at minimum  outlay. The project ’s Strobe out-put (A) provides four brief pulses repeated periodically for the wing  (white strobe) lights. In addition the Beacon output (B) gives a double pulse to drive a red LED for indicating the aircraft’s active operational status. On the proto-type this is usually a red rotating  beacon known as an Anti-Collision Light (ACL). The circuit is equally useful for road vehicle modellers, who can use it to flash headlights and blue emergency lights.

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Lighting Up Model Aircraft

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All signals are generated by a 4060 14-stage binary counter and some minimal output selection logic. Cycle time is determined by the way the internal oscillator is con-figured (resistor and capacitor on pins 9/10) and can be varied within quite broad limits. High-efficiency LEDs are your first choice for the indicators connected to the Bea-con and Strobe outputs (remember to fit series resistors appropriate to the operating voltage Ub and the current specified for the LED used).
The sample circuit is for operating voltages between 5 and 12 V. Cur- rent flow through the two BS170 FET devices must not exceed 500 mA.

Cheap Bicycle Alarm Schematics Circuit

The author wanted a very cheap and simple alarm for some of his possessions, such as his electrically assisted bicycle. This alarm is based on a cheap window alarm, which has a time-switch added to it with a 1-minute time-out. The output  pulse of the 555 replaces the reed switch in the window alarm. The 555 is triggered by a sensor mounted near the front  wheel, in combination with a magnet that is mounted on the spokes. This sensor and the magnet were taken from a cheap bicycle computer.

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Cheap Bicycle Alarm Schematics Circuit

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The front wheel of the bicycle is kept unlocked, so that the reed  switch closes momentarily when the wheel turns. This  triggers the 555, which in turn activates the window alarm. The circuit around the 555 takes very little current and can  be powered by the batteries in the window alarm.  There  is just enough room  left inside the enclosure of the window  alarm to mount the time-switch inside it.
The result is a very cheap, compact device, with only a single cable going to the reed switch on the front wheel. And the noise this thing produces is just unbelievable! After about one minute the noise stops and the alarm goes back into standby mode. The bicycle alarm should be mounted in an inconspicuous place, such as underneath the saddle, inside a (large) front light, in the battery compartment, etc.
Hopefully the alarm scares any potential thief away, or at least it makes other members of the public aware that something isn't quite right.
Caution. The installation and use of this circuit may be subject to legal restrictions in your country, state or area.

Auto Focus for Slide Projector

 

This circuit is intended as a replacement for the electronics in a partly or wholly defective autofocus driver in a slide projector. The mechanical parts in the autofocus system are assumed to be still functional.

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Auto Focus for Slide Projector

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Most automatic focusing systems in slide projectors  are based on the use of an optical module, which comprises a small lamp, a few lenses and mirrors, and a light sensor made from two series connected light dependent resistors (LDRs), which function as a potential divider. As shown in Fig. 1, lamp La projects a narrow beam onto the centre of the slide, A, whose surface reflects it onto the LDRs. When the slide surface bulges inside or outside, the projected image on the screen is blurred, and the beam from L is received on the surface of one of the LDRs (point 2 or 3). This is detected by a motor driver circuit, which ensures that the focal distance between the objective, 0, and the slide surface is corrected to maintain a sharp image, i.e., the objective is moved until the circuit detects that the reflected beam from L falls exactly in between the LDRs.

 The circuit is based on the use of an existing set of  LDRs as part of the optical module in the slide projector. The symmetrical supply shown to the left,  and the motor plus decoupling capacitor, are also part of the projector. The inverting input of opamp IC1  is at ground potential when the above mentioned test beam falls in between the LDRs. The output of the opamp keeps the non-inverting input at 0 V as well, so that no motor voltage is available  at the emitters of power drivers Ti T2. Should the  reflected beam illuminate either one of the LDRs, the circuit arranges for the motor to move the objective glass towards the correct focal position, until no  voltage difference between the LDRs is detected.  The feedback gain of the circuit has been kept relatively low to keep the motor from continuously moving the objective glass past the target position, causing the system to oscillate slowly. Resistors R3 and R4 may have to be dimensioned differently than shown to achieve optimum response as regards speed and stability.

Oil Temperature Gauge for 125 cc Scooter

Lots of Far-Eastern scooters are fitted with GY6 engines. These already elderly units are sturdy and economical, but if you want to  “push” the power a bit (so called ‘Racing’  kits, better handling of the advance, etc.), you soon find yourself faced with the problem  of the engine temperature, and it becomes essential to f it a heat sink (of ten wrongly  referred to as a ‘radiator’) on the oil circuit. Even so, in these circumstances, it’s more than reassuring for the user to have a constant clear indication of the oil temperature. Here are the specifications we set for the temperature gauge we wanted to build:

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Oil Temperature Gauge for 125 cc Scooter

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• no moving parts (so not meter movement), as scooters vibrate a lot!;
• as cheap as possible (around £12);
• robust measuring transducer (avoid NTC thermistors and other ‘exotic’ sensors);
• temperature range 50–140 °C. (122 – 291 °F);
• audible and visual warning in case of dangerous temperature;
• compact;
• waterproof.

Let’s start by the sensor. This is a type-K thermocouple, as regularly used by multimeter manufacturers. Readily available and fairly cheap, these are robust and have excellent linearity over the measurement range we’re interested in here. The range extends from 2 mV to 5.7 mV for ten measurement points. The positive output from the thermocouple is applied to the non-inverting input of IC3.A,  wired as a non-inverting amplifier. Its gain  of 221 is determined by R1 and R2. IC3 is an LM358, chosen for its favourable characteristics when run from a single-rail supply. IC3.B is wired as a follower, just to avoid leaving it powered with its pins floating.
IC3.B output is connected to pin 5 of IC1, an LM3914. This very common IC is an LED display driver. We can choose ‘point’ or ‘bar’ mode operation, according to how pin 9 is connected. Connected as here to the + rail, the display will be in ‘bar’ mode. Pin 8, connected to ground, sets the full scale to 1.25 V. R3 sets the average LED current. Pin 4, via the potential divider R7/R8+R9, sets the offset  to 0.35 V. Using R8 and R9 in series like this avoids the need for precision resistors.
As per the LM3914 application sheet , R4-R5-R6 and C5 will make the whole display flash as soon as D10 lights (130 °C = 226 °F). Simultaneously, via R10 and T1, the (active) sounder will warn the user of overheating. Capacitor C6 avoids undesirable variations in the reference voltage in ‘flashing’ mode. IC2 is a conventional 7808 regulator and C1– C4 filter the supply rails. Do not leave these out! D1 protects the circuit against reverse polarity.
The author has designed two PCBs to be fit-ted as a ‘sandwich’ (CAD file downloadable  from [1]). In the download you’ll also find  a document with a few photos of the project. You’ll note the ultimate weapon in on-board electronics: hot-melt glue. Better than epoxy (undoable!) and quite effective against vibration.