Monday, September 30, 2013

AFX Slot Car Lap Counter

AFX slot car sets are very enjoyable but you can increase the fun with a lap counter. This circuit will count from 00 to 99, with independent counters for each track. The sensing device used is a Hall effect sensor (UGN3503; available from Dick Smith Electronics). One of these sensors is glued under a section of each track (printed side up); between the slot and one of the track rails is the best spot. In this position, it will allow the ground effects magnets on the cars to pass over them. The sensor will provide a voltage of about 3V when a car passes over it and about 2V without a magnetic field. Both counter circuits are identical, with dual op amp IC5 handling the signals from both sensors.

AFX slot car lap counter circuit schematic

IC5a and IC5b are wired as comparators, with a 2.5V reference derived from zener diode ZD1 via the 10kO and 12kO resistors. Each time the output of IC5a goes high it clocks IC1a, a 4518 BCD counter. NAND gates IC2a & IC2b provide a carry out to the other half of IC1 for a 2-digit display. More counters may be cascaded this way to provide extra digits. The BCD outputs of IC1 drive 7-segment decoders IC3 & IC4 which drive common cathode LED displays. Push-button S1 resets the counters to 00 for both tracks for the start of a new race.
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Sunday, September 29, 2013

Pulse Generator

This circuit is very useful while checking/operating counters, stepping relays, etc. It avoids the procedure of setting a switch for the required number of pulses. By pressing appropriate switches S1 to S9, one can get 1 to 9 negative-going clock pulses, respectively. Schmitt trigger NAND gate N1 of IC2, resistor R1, and capacitor C1 are wired to produce clock pulses. These pulses are taken out through NAND gate N3 that is controlled by decade counter CD4017 (IC1). Initially no switch from S1 to S9 is depressed and the LED is glowing. As pins 5 and 6 of NAND gate N2 are pulled up by resistor R3, its output pin 4 goes low. This disables NAND gate N3 to take its output pin 10 to high state, and no pulse is available. IC1 is a decade counter whose Q outputs normally remain low.

When clock pulses are applied, its Q outputs go high successively, i.e. Q0 shifts to Q1, Q1 shifts to Q2, Q3 shifts to Q4, and so on. If any one of switches S1 through S9, say, S5 (for five pulses), is momentarily depressed, pins 5 and 6 of NAND gate N2 go low, making its output pin 4 high, which fully charges capacitor C2 via diode D. At the same time, this high output of N2 enables NAND gate N3 and clock pulses come out through pin 10. These are the required number of pulses used to check our device. The clock pulses are fed to clock-enable pin 13 of IC1, which starts counting. As soon as output pin 1 (Q5) of IC1 turns high, input pins 5 and 6 of NAND gate N2 will also become high via switch S5 because high-frequency clock allowed five pulses during momentary pressing.

Pulse Generator circuit diagramThis high input of N2 provides low output at pin 4 to disable NAND gate N3 and finally no pulse will be available to advance counter IC1. Before the next usage, counter IC1 must be in the standby state, i.e. Q0 output must be in the high state. To do this, a time-delay pulse generator wired around NAND gate N4, resister R4, diode D, capacitor C2, and differentiator circuit comprising C3 and R5 is used. When output pin 4 of NAND gate N2 is low, it discharges capacitor C2 slowly through resistor R4. When the voltage across capacitor C2 goes below the lower trip point, output pin 11 of NAND gate N4 turns high and a high-going sharp pulse is produced at the junction of capacitor C3 and resistor R5.

This sharp pulse resets counter IC1 and its Q0 output (pin 3) goes high. This is represented by the glowing of LED. Ensure the red LED is glowing before proceeding to get the next pulse. Press any of the switches momentarily and the LED will glow. If the switch is kept pressed, the counter counts continuously and you cannot get the exact number of pulses.
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Saturday, September 28, 2013

The Gentle Touch Circuit Diagram

Consumer appliances these days hardly ever have a proper mains switch. Instead, appliances are turned on and off at the touch of a button on the remote control, just like any other function. This circuit shows how a device (as long as it does not draw too high a current) can be switched on and off using a pushbutton. The approach requires that a microcontroller is already available in the circuit, and a spare input port pin and a spare output port pin are required, along with a little software. When power is applied T1 initially remains turned off. When the button is pressed the gate of T1 is taken to ground and the p-channel power MOSFET conducts. The microcontroller circuit is now supplied with power. Within a short period the microcontroller must take output PB1 high. This turns on n-channel MOSFET T1 which in turn keeps T1 turned on after the push-button is released.

Now the microcontroller must poll the state of the push-button on its input port (PB0) at regular intervals. Immediately after switch-on it will detect that the button is pressed (a low level on the input port pin), and it must wait for the button to be released. When the button is next pressed the device must switch itself of f: to do this the firmware running in the microcontroller must set the output port pin to a low level. When the button is subsequently released T1 will now turn off and the supply voltage will be removed from the circuit.

The circuit itself draws no current in the off state, and for (rechargeable) battery-powered appliances it is therefore best to put the switch before the voltage regulator. For mains-powered devices the switch can also be fitted before the voltage regulator (after the rectifier and smoothing capacitor). Since there is no mains switch there will still be a small standby current draw in this case due to the transformer. Be careful not to exceed the maximum gate-source voltage specification for T1: the IRFD9024 device suggested can withstand up to 20 V. At lower voltages R2 can be replaced by a wire link; otherwise suitable values for the voltage divider formed by R1 and R2 must be selected.

Circuit diagram:

the-gentle-touch-circuit-diagramw The Gentle Touch Circuit Diagram

The author has set up a small website for this project at http://reweb.fh-weingarten.de/elektor, which gives source code examples (which include dealing with pushbutton contact bounce) for AVR microcontrollers suitable for use with AVR Studio and GNU C. Downloads are also available at http://www.elektor.com.

Rainer Reusch - Elektor Electronics 2008

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Friday, September 27, 2013

Three Hour Timer

Manufacturers of cordless drills generally recommend a battery charging time of three hours. Once the charging time is up the battery must be disconnected from the charger: if you forget to do this there is a danger of overcharging the battery. This circuit, which sits between the charger circuit and its battery socket, prevents that possibility: the contact of relay Re1 interrupts the charging current when the three hours are up. Ten LEDs show the remaining charging time in steps of 20 minutes. The timer is reset each time power is applied and it is then ready for a new cycle. When power is applied IC3 is reset via C4 and R5. When the charging time has elapsed, Q9 (pin 11) goes high, which turns the relay on and interrupts the charging current.

Three Hour Timer Circuit DiagramSince Q9 is connected to the active-low EN (enable) input, the counter will now remain in this state. The charging time can be adjusted from about 2 hours 15 minutes to 4 hours 30 minutes using P1. The author set P1 to 30 kΩ, giving a charging time of 3 hours 7minutes. The greater the resistance of P1, the shorter the charging time. The timing of the circuit is not particularly precise, but its accuracy is entirely adequate for the job. When adjusting the charging time it is worth noting that the first clock cycle after the circuit is turned on (from Q0 to Q1) is longer than the subsequent ones. This is because initially capacitor C3 has to be charged to around half the supply voltage.
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Wednesday, September 25, 2013

Infra Red Remote Control Tester

This little circuit is invaluable for quick go/no-go testing of just about any remote control transmitting infra-red (IR) light. The tester is battery-powered, built from just a handful of commonly available and inexpensive parts, and fits in a compact enclosure. Schmitt trigger gate IC1f is used as a quasi-analogue amplifier with, unusually, an infra-red emitting diode (IRED) type LD274 acting as the sensor element. An R-C network, C1-R2, is used at the output of the gate because all IR remote controls transmit pulse bursts, and to prevent the output LED, D2, lighting constantly when day-light or another continuous source of IR light is detected.

Circuit diagram:



Cased project:
This creates a useful ‘quick test’ option: point the tester at direct daylight, and the indicator LED should light briefly. The sensitivity of the tester is such that IR light from remote control is detected at a distance of up to 50 cm. The circuit is designed for very low power consumption, drawing less than 1 mA from the battery when IR light is detected, and practically no current when no light is detected. Hence no on/off switch is required. The construction drawing shows how the tester may be ‘cased’ using a small ABS case from Conrad.

COMPONENTS LIST
Resistors:
R1,R2 = 10MW
Capacitor:
C1 = 10nF
Semiconductors:
D1 = LD274 (Siemens)
D2 = LED, 3mm, low-current
IC1 = 74HC14
Miscellaneous:
Bt1 = 3V Lithium cell with solder tags, e.g.type CR2045 (560 mAh)
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Tuesday, September 24, 2013

Infra red Light Barrier Using 555

This is a short-range light barrier for use as an intruder alarm in doorposts, etc. The 555 in the transmitter (Figure 1) oscillates at about 4.5 kHz, supplying pulses with a duty cycle of about 13% to keep power consumption within reason. Just about any infra-red LED (also called IRED) may be used. Suggested, commonly available types are the LD271 and SFH485. The exact pulse frequency is adjusted with preset P1. The LEDs are pulsed at a peak current of about 100 mA, determined by the 47 Ω series resistor. In the receiver (Figure 2), the maximum sensitivity of photo-diode D2 should occur at the wavelength of the IR LEDs used in the transmitter. You should be okay if you use an SFH205F, BPW34 or BP104. Note that the photo-diode is connected reverse-biased! So, if you measure about 0.45 V across this device, it is almost certainly fitted the wrong way around.

transmitter Infra-red Light Barrier Circuit DiagramThe received pulses are first amplified by T1 and T2. Next comes a PLL (phase lock loop) built with the reverenced NE567 (or LM567). The PLL chip pulls its output, pin 8, Low when it is locked onto the 4.5 kHz ‘tone’ received from the transmitter. When the (normally invisible) light beam is interrupted (for example, by someone walking into the room), the received signal disappears and IC1 will pull its output pin High. This enables oscillator IC2 in the receiver, and an audible alarm is produced. The two-transistor amplifier in the receiver is purposely over-driven to some extent to ensure that the duty cycle of the output pulses is roughly 50%.

Receiver Infra-red Light Barrier Circuit DiagramIf the transmitter is too far away from the receiver, over-driving will no longer be guaranteed, hence IC1 will not be enabled by an alarm condition. If you want to get the most out of the circuit in respect of distance covered, start by modifying the value of R2 until the amplifier output signal again has a duty cycle of about 50%. The circuit is simple to adjust. Switch on the receiver, the buzzer should sound. Then switch on the transmitter. Point the transmitter LEDs to the receiver input. Use a relatively small distance, say, 30 cm. Adjust P1 on the transmitter until the buzzer is silenced. Switch the receiver off and on again a few times to make sure it locks onto the transmitter carrier under all circumstances. If necessary, re-adjust P1, slowly increasing the distance between the transmitter and the receiver.
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Monday, September 23, 2013

Video Amplifier

The video amplifier in the diagram is a well-known design. Simple, yet very useful, were it not for the ease with which the transistors can be damaged if the potentiometers (black level and signal amplitude) are in their extreme position. Fortunately, this can be obviated by the addition of two resistors. If in the diagram R3 and R4 were direct connections, as in the original design, and P1 were fully clockwise and P2 fully anticlockwise, such a large base current would flow through T1 that this transistor would give up the ghost.

Video Amplifier Circuit DiagramMoreover, with the wiper of P2 at earth level, the base current of T2 would be dangerously high. Resistors R3 and R4 are sufficient protection against such mishaps, since they limit the base currents to a level of not more than 5mA. Shunt capacitor C4 prevents R4 having an adverse effect on the amplification.
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Sunday, September 22, 2013

Master Slave Switch

In this age of enlightenment any sort of relationship that could be described as master/slave would be questionable but for the purposes of this circuit it gives a good idea of how it functions. The circuit senses mains current supplied to a ‘master’ device and switches ‘slave’ equipment on or off. This feature is useful in a typical hi-fi or home computer environment where several peripheral devices can all be switched on or off together. A solid-state relay from Sharp is an ideal switching element in this application; a built-in zero crossing detector ensures that switching only occurs when the mains voltage passes through zero and any resultant interference is kept to an absolute minimum.

Master/Slave Switch Circuit Diagram circuit schematic

All of the triac drive circuitry (including optical coupling) is integrated on-chip so there are very few external components and no additional power supply necessary. This makes the finished design very compact. Diodes D1, D2, D3 and D4 perform the current sensing function and produce a voltage on C2 when the master equipment is switched on. A Schottky diode is used for D5 to reduce forward voltage losses to a minimum. The circuit is quite sensitive and will successfully switch the slave even when the master equipment draws very little mains current. The RC network formed by R1 and C1 provides some protection for the solid-state relay against mains-borne voltage transients.

Warning:
This circuit is connected to the mains. it is important to be aware that the chip has lethal voltages on its pins and all appropriate safety guidelines must be adhered to! This includes the LED, for safety it must be fitted behind a transparent plexiglass shield.
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Friday, September 20, 2013

1994 Saturn sedan 1 9L Wiring Diagram

1994 Saturn sedan 1.9L Wiring Diagram
(click for full size image)

The Part of 1994 Saturn sedan 1.9L Wiring Diagram: cluth start switch, underhood junction block, nuetral start switch, ignition switch, power distribution, generator, fusible link, starter solenoid, near battery,
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Wednesday, September 11, 2013

4A High Speed Low Side Gate Driver Circuit

 The UCC27518 and UCC27519 single-channel, high-speed, low-side gate driver device is capable of effectively driving MOSFET and IGBT power switches. Using a design that inherently minimizes shoot-through current, UCC27518 and UCC27519 are capable of sourcing and sinking high, peak-current pulses into capacitive loads offering rail-to-rail drive capability and extremely small propagation delay typically 17 ns.

  4A High-Speed Low-Side Gate Driver Circuit

 4A High-Speed Low-Side Gate Driver Circuit


 The UCC27518 and UCC27519 provide 4-A source, 4-A sink (symmetrical drive) peak-drive current capability at VDD = 12 V. The UCC27518 and UCC27519 are designed to operate over a wide VDD range of 4.5 V to 18 V and wide temperature range of -40°C to 140°C. Internal Under Voltage Lockout (UVLO) circuitry on VDD pin holds output low outside VDD operating range.


Features
  • Low-Cost, Gate-Driver Device Offering Superior Replacement of NPN and PNP Discrete Solutions
  • Pin-to-Pin Compatible With TI’s TPS2828 and the TPS2829
  • 4-A Peak Source and 4-A Peak Sink Symmetrical Drive
  • Fast Propagation Delays (17-ns typical)
  • Fast Rise and Fall Times (8-ns and 7-ns typical)
  • 4.5-V to 18-V Single Supply Range
  • Outputs Held Low During VDD UVLO (ensures glitch free operation at power-up and power-down)
  • CMOS Input Logic Threshold (function of supply voltage with hysteresis)
  • Hysteretic Logic Thresholds for High Noise Immunity
  • EN Pin for Enable Function (allowed to be no connect)
  • Output Held Low when Input Pins are Floating
  • Input Pin Absolute Maximum Voltage Levels Not Restricted by VDD Pin Bias Supply Voltage
  • Operating Temperature Range of -40°C to 140°C
  • 5-Pin DBV Package (SOT-23)
Device Uses
  • Switch-Mode Power Supplies
  • DC-to-DC Converters
  • Companion Gate Driver Devices for Digital Power Controllers
  • Solar Power, Motor Control, UPS
  • Gate Driver for Emerging Wide Band-Gap Power Devices (such as GaN)
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Tuesday, September 10, 2013

Typical Oil Cooler Assemblies Air Oil wirh Hydraulic Fan Water Oil



Typical Oil Cooler Assemblies Air Oil wirh Hydraulic Fan Water Oil
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Wednesday, September 4, 2013

IR Remote Control Extender Mark 3

This Mark3 version of the Infra Red extender is a special version designed to control appliances that use high frequency modulated IR remote controls.


Notes:
IR appliances use pulses (control signals) sent over a modulated IR carrier wave. The carrier wave may be modulated at various frequencies, 36-38KHz being the most popular.Some Satellite receivers use even higher frequencies than this. The IR1 remote module receives an infra red signal and separates control pulses from the modulation. To re-transmit, a 555 timer is configured as an astable oscillator. The 555 timer is controlled by the signal on the reset pin, high generating a carrier and low no carrier. Each control pulse turns on the oscillator for the duration of a logic high signal and off for a logic 0 signal, thereby creating a newly modulated IR signal. The IR module, part number IR1 is available from Harrison Electronics in the UK, IR1 may not be listed in their catalogue but if you ask for an IR1, they will send you the correct part. The IR1 arrives in a small aluminium case, the connections viewed from underneath are shown below:

Infra Red Module, IR1 Pinout

Harrison Electronics have limited supplies of the IR1 but as a replcement a standard IR module like the TSOP1838 may be used. The pinout is shown below:


The carrier frequency is determined by R1 and C3, values shown work at 39.7 kHz, but these may be altered to provide different carrier frequencies. The final CMOS 4049 invertor ensures that under "no signal" conditions both LEDs are also off.

Parts List:

C1 100u 10V
C2 100n polyester
C3 120p silver mica
C4 100n polyester
R1 150k
R2 2k2k
R3 1k
R4 47R 1W
Q1 BC109C
IC1 LM7805
IC2 555
IC3 IR1 module from Harrison Electronics or TSOP1838
IC4 4049 CMOS Invertor LED1 Red LED (or any visible colour)
LED2 TIL38 or part YH70M from Maplin Electronics


PCB Layout (courtesy of Claudio from Italy):
First the component side of the board is shown below.


And now thw pcb itself.

The Mark 3 circuit is an improvement over the Mark 1 and 2 circuits, however the drive from Q1 inverts the polarity of the output pulse. In some cases this can cause problems so the output stage is rewired as an emitter follower. This is the basis for the Mark 4 circuit. If you still have problems then I would recommend trying the Mark 4 circuit.

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Tuesday, September 3, 2013

Transistor Water Sensor Alarm

This water sensor alarm circuit diagram is designed using common electronic components. Thewater sensor alarm circuit may operate an active buzzer, to make a sound when is reached a certain level of water.

Transistor Water Sensor Alarm Circuit Diagram


Because water sensor and control circuit for buzzer are located on the same printed circuit board, indicator, together with 9 V battery and buzzer can be mounted in a compact case.

When water reaches the sensor, the base of T1 is connected to the positive supply terminal. Therefore, T1 and T2 are open, so that buzzer BZ1, will be activated. Sensitivity reduction of the circuit can be done by increasing the value of R2.
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Sunday, September 1, 2013

Q Multiplying Loop Antenna

 Q-Multiplying Loop Antenna Schematic



Notes
This circuit is designed to be used in conjunction with the standard 4 foot square loop used in MW for long distance reception.

Circuit : David Sayles
Email: All enquiries via anc@mitedu.freeserve.co.uk 

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