Monday, May 30, 2011
Infrared Radar (IR) System
Infrared Radar (IR) SystemChris from PyroElectro.com has a abundant commodity about a do-it-yourself alarm arrangement body with PIC18F452. It’s a abundant amusement activity although the schematic is actual complicated. This activity uses three capital accessories to actualize the claimed alarm system. The IR Ambit sensor gives output, the pic microcontroller processes it and again displays the achievement on the led array.
The ambition of this activity is to actualize a alive ir alarm system. The arrangement will alone be appropriate to admeasurement abutting adjacency at an bend of 90 degrees as apparent in the archetype above. The ambit of arrangement is almost 4-30cm, 20-150cm & 1m-5.5m depending aloft which sensor you accept to use. Below is an archetype of what abbreviate ambit claimed alarm could be acclimated for.
Thursday, May 26, 2011
Hot Water Indicator Using NTC Thermistors
A simple circuit to indicate various levels of hot water in a tank. SW1 is a normally open press button switch which allows you to view the level of hot water in a hot water tank. When pressed the voltage difference at the junction of the thermistor and preset is compared to the fixed voltage on the op-amps non-inverting input. Depending on the heat of the water in the tank, the thermistors resistance will toggle the op-amp output to swing to almost full voltage supply and light the appropriate LED.
With a full tank
of hot water adjust P1-4 so that all LED's are lit. As hot water rises,
the sensor at the bottom of the tank will be the maximum level of hot
water. "Hot" can be translated as 50C to 80C the presets P1-4 allow
adjustment of this range.
Parts:
- I have used a quad version of the LM324 but any quad opamp can be used or even four single op-amps.
- R2-R5 I used 330ohm resistors, but value is not critical. Lower values give brighter LED output.
- NTC1-4 The thermistors maximum resistance must roughly equal the resistance of the fixed resistor and preset. As negative temparature coefficient (NTC) thermistors are used, then their resistance decreases for increases in temperature. I used a thermistor from the Maplin Catalogue. Cold resistance was around 300K, hot resistance 15k. Alternative thermistors may be used with different resistance ranges, but the presets P1 to P4 must also be changed as well.
- R7-10 series resistance, only required if your thermistors resistance is several ohms at the hottest temperature.
- P1 - P4 Chosen to match the resistance of the thermistor when cold.
- R1 & R6. These resistors are equal and bias the op-amp inverting input to half the supply voltage. I used 100k.
This hot water indicator circuit from : zen22142.zen.co.uk
Tuesday, May 24, 2011
Long Delay Timer Using IC 4011 Nand Gates
This following circuit shows a Long Delay Timer Circuit Diagram. This circuit designed mainly to switch off a portable radio after some time:
A very long time constant is provided by R1 and C1. C1 discharges and the near zero voltage at its positive lead is applied to the high impedance inputs of the four gates of IC1 wired in parallel when P2 is momentarily closed. The battery voltage is available at Q1 Emitter since the four paralleled gate outputs of the IC go therefore to the high state.
The circuit will start if P2 is pushed for 1 to 5 second and will switch off after about 35 minutes. The time delay can be varied depends on values of R1 and/or C1. If required, P1 will stop the timer. LED D1 is optional. When the load is placed far from the time, LED D1 can be useful to signal relay operation
List Components of Long Delay Timer Circuit :
R1 : 10M R2 : 4K7 R3 : 1K C1 : 220µF/25V D1 : LED any type D2 : 1N4148 IC1 : 4011 Quad 2 Input NAND Gate CMos IC Q1 : BC337 P1,P2: SPST Pushbuttons RL1 : 12V Relay Switch
3-Phase Pulse Generator Using CMOS Inverters And Shift Register
Adjustable Switching Regulator using LM317
A switching voltage regulator circuit shown here can be a low cost solution for your high efficiency requirement electronic circuit design. This regulator circuit can deliver up to 3A of current. The input voltage range of this circuit is between 8 to 35V DC and the output voltage can be adjusted between 1.8 to 32V DC. The output voltage can be adjusted by using the POT R4
The circuit uses a standard linear regulator LM317 IC. LM317 regulator IC provide a stable internal voltage reference, and provide the adjustment method. This wide-range output voltage adjustment make it suitable for general purpose power supply in lab application.
When compared to linear voltage regulators the switching voltage regulators are much power efficient. In the case of linear voltage regulators the difference between the input and output voltage is just wasted and for switching regulators there is almost no such wastage and that’s why the switching regulators have great power efficiency ranging up to 85% . In simple words, the switching regulator operates by taking small bits of energy from the input voltage source and then transferring it to the output with the help of a solid state switch and a control circuitry. Since the switching element is either fully open or closed at any moment, no energy is wasted across it. The control circuit controls the duty cycle of the solid state switch which in turn determines rate at which energy is transferred to the output.
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