Showing posts with label Electronic Control. Show all posts
Showing posts with label Electronic Control. Show all posts
Saturday, July 7, 2007
Friday, June 1, 2007
DC Motor Control Circuit
Notes:Here, S1 and S2 are normally open , push to close, press button switches. The diodes can be
red or green and are there only to indicate direction. You may need to alter the TIP31 transistors
depending on the motor being used. Remember, running under load draws more current. This
circuit was built to operate a small motor used for opening and closing a pair of curtains. As an
advantage over automatic closing and opening systems, you have control of how much, or how
little light to let into a room. The four diodes surriunding the motor, are back EMF diodes. They
are chosen to suit the motor. For a 12V motor drawing 1amp under load, I use 1N4001 diodes.
Frost Alarm or Cold Activated Switch by IC 741
Circuit : Andy Collinson
Email: anc@mitedu.freeserve.co.uk
Description:
A simple thermistor triggered cold switch with adjustable threshold.
Notes:
The thermistor used has a resistance of 15k at 25 degrees and 45k at 0 degrees Celsius. A suitable bead type thermistor can be found in the Maplin catalogue. The 100k pot allows this circuit to trigger over a wide range of temperatures.
If using a different thermistor then the control should match the new thermistor at its highest resistance, or be higher in value. The op-amp in this circuit is the ubiquitous 741. It may be catalogued as LM741, CA741 etc, all types will work. In this circuit it is used as a comparator. The non-inverting input (pin 3) is biased to half the supply voltage. The non-inverting input is connected to the junction of the thermistor and potentiometer. The control is adjusted so that the circuit is on when the thermistor is at the required temperature range. Once the thermistor is outside the temperature range its resistance alters and the op-amp output changes from near full supply to around 1 or 2 volts dc. There is insufficient voltage to turn on the transistor and the relay will not energise.
A slight amount of hysteresis is provided by inclusion of the 270k resistor. This prevents rapid switching of the circuit when the temperature is near to the switching threshold.
Wednesday, May 30, 2007
Voltage Controlled Switch using 555 Timer
Source :: http://www.zen22142.zen.co.uk/Circuits/Switching/vcs555.htm
Circuit : Miroslav Adzic - Serbia & Montenegro
Description:
In this circuit the 555 timer is used in a novel way, as a voltage controlled switch.
Notes:
The old and omnipresent NE555 can be very good at something it was not meant for: driving relays or other loads up to 200 mA. The picture shows an example circuit: if the input level rises over 2/3 of the supply voltage - it will turn on the relay, and the relay will stay on until the level at the input drops below one third of the supply voltage.
If the relay and D1 were connected between pin 3 and ground, the relay would be activated when the input voltage drops below one third, and deactivated when the input voltage goes over two thirds of the supply voltage.
It is also a nice advantage that the input requires only about 1 uA, which is something bipolar transistors can't compete with. (This high impedance input must not be left open.) A large hysteresis makes the circuit immune to noise. The output (pin 3) can only be either high or low (voltage-wise), and it changes its state almost instantenously, regardless of the input signal shape.
The voltage drop across the NE555's output stage (at 35-100 mA) is 0.3-2.0 V, depending on the way the relay is connected and the exact current it draws. D1 is absolutely vital to the safety of the integrated circuit.
Circuit : Miroslav Adzic - Serbia & Montenegro
Description:
In this circuit the 555 timer is used in a novel way, as a voltage controlled switch.
Notes:
The old and omnipresent NE555 can be very good at something it was not meant for: driving relays or other loads up to 200 mA. The picture shows an example circuit: if the input level rises over 2/3 of the supply voltage - it will turn on the relay, and the relay will stay on until the level at the input drops below one third of the supply voltage.
If the relay and D1 were connected between pin 3 and ground, the relay would be activated when the input voltage drops below one third, and deactivated when the input voltage goes over two thirds of the supply voltage.
It is also a nice advantage that the input requires only about 1 uA, which is something bipolar transistors can't compete with. (This high impedance input must not be left open.) A large hysteresis makes the circuit immune to noise. The output (pin 3) can only be either high or low (voltage-wise), and it changes its state almost instantenously, regardless of the input signal shape.
The voltage drop across the NE555's output stage (at 35-100 mA) is 0.3-2.0 V, depending on the way the relay is connected and the exact current it draws. D1 is absolutely vital to the safety of the integrated circuit.
Tuesday, May 22, 2007
Circuit Video Amplifier by transistor BC547 & BC557
Circuit Video Amplifier by transistor BC547 & BC557
PCB Video Amplifier by transistor BC547 & BC557Circuit Sound SCR Swith by IC 1458 & SCR C106D
Circuit Sound SCR Swith by IC 1458 & SCR C106D
PCB Sound SCR Swith by IC 1458 & SCR C106D
Circuit Light Relay Switch By BC547 & BC337
Circuit Light Relay Switch By BC547 & BC337
PCB Light Relay Switch By BC547 & BC337
Friday, May 18, 2007
Dfferential Temperature Relay Switch by IC 741
Circuit Dfferential Temperature Relay Switch by IC 741
Thursday, May 17, 2007
Monday, May 14, 2007
Monday, May 7, 2007
Thursday, April 19, 2007
Electronic car ignition
Description:
This scheme is for 4 cylinder motor. This will make your car spent less fuel, be a little bit faster and you won�t have to frequently open your distributor cap to change the contact buttons thus wasting less money.
T1/T2 create one monostable multivibrator in which C2 and R5 determine the length of impulse which is 1,5 msec. Next in line are T3 and then T4 which is Darlington transistor specially developed for electronic ignition which is used as a switch to turn on/off primary coil. Impulses from switch P turn on monostable multivibrator T1/T2. You need to un-connect capacitor that is in distributor cap because it is not needed anymore. While switch P is closed T1 is in off state but T2 is in on state, also T3 and T4 which enables current to flow trough primary coil. When switch P is opened, T1 gets in on state for a moment causing C2 to charge over R6 which makes T2 go to off state because of voltage drop on R6. When T2 is off also T3 and T4 are off and current that was flowing trough primary coil is stopped. Because T2 is in off state, voltage on R8 is increased which is passed trough R5 on T1 base which is still in on state and C2 is still charging. After 1,5 msec. C2 value reaches the level where T2 goes to on state again and T1 goes to off state. Now T2, T3 and T4 are in on state, again, and current flows trough primary coil again. R2 and D1 are used to neutralize the effect of impulses caused from «jumping» of switch P which could turn on monostable multivibrator when it shouldn't.
Zener diodes Z5 and Z6 are together with R10 limit overcharged voltage impulses that are caused by self induction of primary coil which could damage T4. They should be connected as close as possible to T4.
D7 protects device from wrong polarity.
Coil should have ratio of 1:80 or 1:100 with external resistor Rv which is used for better cooling. Total resisting value (Rp) of primary coil and Rv resistor shouldn't be under 1,6 ohm's so current trough T4 wouldn�t be bigger than 10A.
Depending on Rp, R9 have different values:
120Ω/2W for Rp tot > 2,2Ω
100Ω/2W for 1,8Ω <>Parts:
D1-D4 = 1N4148
D5-D6 = BZX85C � 180 (replicable with all equivalent types with power of 1,3W)
D7 = 1N4001
R1 = 470 - 1W
R2 = 22k
R3 = 2,2k
R4 = 1k
R5 = 4,7k
R6 = 39k
R7 � R10 = 100
R8 = 680
C1 � C2 = 47nF (ceramic)
C3 = 0,22uF 400V (ceramic)
C4 = 100uF (electrolytic)
T1 � T2 = BC327 (BC327-25, BC327-40)
T3 = BC237B (BC547B, BC547C)
T4 = BUX37 (BU323, BU920, BU921, BU922, BUV37B (u TOP3), BUW29, BUW81, MJ10012, MJ10013, MJ10014, TIP662, TIP665, 2SD683)
Thursday, February 8, 2007
Touch 'N Flip
Ever wonder how a touch plate, like the kind you see on some elevators and lamps work? This circuit will give you a feel for how the touch plate works in a circuit and you can expand on the circuit to suit your project needs. The touch plate can be a small piece of metal or aluminum foil. Start the circuit by moving S2 to the set position and then back to the previous position. Now press S1. One of the LED's will light. Now touch the touch plate and the LED's will flip on the opposite way. The sensitivity of the plate will vary depending on the humidity. Adjust the VR and capacitor that is connected to S2 to adjust the sensitivity.From : http://home.maine.rr.com/randylinscott/apr21.htm
Friday, February 2, 2007
Electronic Combination Lock
This circuit is very basic to build. To open a the lock which is connected to the K1 Load you must press each momentary switch in the correct sequence. The sequence used in this circuit is S1,S2,S3,S4. If any of the other switches are pressed the circuit will reset and you will need to start over. Depending on how you wire the switches, you can use any 4 switch combination.
Thursday, February 1, 2007
Motor Speed Control
This circuit will allow you to control the speed of an AC motor, for example an electric drill. The way that this circuit works is as follows. The bridge rectifier produces dc voltage from the 120vac line. A portion on this current passes through the 10K ohm pot. The circuit comprised of the 10k pot, the two 100 ohm resistors and the 50uf capacitors delivers gate drive of the SCR. The diode D1 protects the circuit from reverse voltage spikes. The ratings of the bridge rectifier and the SCR should be 25 amps and PIV 600 volts. The diode D1 should be rated for 2 amps with PIV of 600 volts. The circuit can handle a load up to 10 amps. The SCR should be very well heat sinked.
from :: http://home.maine.rr.com/randylinscott/aug99.htm
Subscribe to:
Posts (Atom)