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Tuesday, April 30, 2013

Tri Waveform Generator

The Tri-Waveform Generator can be used for a number of different uses. The one that I use it for is a signal generator to test circuits. The frequency range is 20 to 20khz. and can be adjusted by R1. The duty cycle or the time that the waveform is high and the time that the waveform is low can be adjusted by R4. The purpose of R2 and R3 are to clean up any distortion on the sine wave output. To do this you must hook up the sine wave output to and oscilloscope and adjust R2 & R3 to make the sine wave as accurate as possible.

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Sound Activated Switch II

With this sound activated switch, control by sound may be very useful, not just on a robot but also for a bit of home automation, for example a sound-activated light responding to a knock on the door or a hand clap. The light will be automatically switched off after a few seconds. An alternative use is burglar protection — if someone wants to open the door or break something the light will come on, suggesting that someone’s at home. The circuit can work from any 5–12 VDC regulated power supply provided a relay with the suitable coil voltage is used.

Sound activated switch circuit diagram

Circuit Project: Sound Activated Switch circuit

When you first connect the supply voltage to the sound activated switch circuit, the relay will be energised because of the effect of capacitor C2. Allow a few seconds for the relay to be switched off. You can increase or decrease the ‘on’ period by changing the value of C2. A higher value results in a longer ‘on’ period, and vice versa. Do not use a value greater than 47μF.

Biasing resistor R1 determines to a large extent the microphone sensitivity. An electret microphone usually has one internal FET inside which requires a bias voltage to operate. The optimum bias level for response to sound has to be found by trial and error. All relevant electrical safety precautions should be observed when connecting mains powered loads to the relay contacts.

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Friday, April 26, 2013

Voltage Regulators Protector

People ceaselessly fail to remember that many voltage regulator ICs have an upper restrict (usually 35 V) on the input voltage they are able to deal with. That applies essentially to sorts with a fixed output voltage. Adjustable voltage regulators actually have a maximum voltage specification, in that case between the enter and output (commonly forty V). The enter voltage should as a result be limited to that stage in a fault situation through which the output is briefed. This circuit presentations a solution to enable such regulators for use in state of affairss with greater input voltages. Although the answer includes an extra three parts, it is easy and can also be constructed using usually available components.

The voltage throughout the regulator is restricted by using the mix of T1 and zener diode D1 to a price that lets the regulator to work properly with loads up to the most rated load. R1 professionalvides an enough operating present for D1 and the bias present for T1. It’s a excellent suggestion to use a Darlington kind for T1 to be able to maintain the worth of R1 reasonably excessive. The current thru D1 is simplest 10 mA with an enter voltage of 60 V. Naturally, we additionally measured what the circuit does when no load is connected. Surprisingly sufficient, the nominal output voltage of 5.02 V increased to best 5.10 V (with a 60-V input voltage). In our scans, we used a BDV65B for T1 and a value of 4.7 kΩ for R1.

If you are having a look to have to be sure that the circuit is really brief-circuit professionalof with an enter voltage of 60 V, you should use a transistor that is still within its safe working house at the maximum enter voltage with the brief circuit current of the regulator (which can exceed 2 A). The BDV65B and TIP142 do not meet this requirement. The maximum voltage for the BDV65B is actually 40 V, and for the TIP142 is 50 V. If the transistor spoils down, the regulator may even spoil down. We verified that experimentally. One risk is so as to add SOA professionaltection for T1, but that quantitys to professionaltecting the professionaltection. Another possibility is to chill out the requirements.

For that objective, R1 must provide enough current to ensure that T1 receives enough current in the event of a brief circuit to maintain the voltage across T1 decrease, however that doesn’t make various distinction in apply, and it additionally increases the minimal load. Besides that, it should be evident that adequate cooling for T1 and IC1 should be provided in maintaining with the load. Ripple suppression is only marginally littered with the professionaltection circuit, since the enter is already neatly stabilised by T1, however the current via D1 does go with the flow in the direction of the output. The presence of C2 should even be taken into account.

In this circuit, with an adjustable voltage regulator one of theses the LM317 and an output voltage greater than 40 V, C2 will cause the voltage to be in brief larger than 40 V in the experience of a brief circuit, which can additionally result in the IC to be damaged. In that case, it'll be important to discover a completely different solution or use a distinct type of voltage regulator.

Circuit Source: DIY Electronics Projects

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Sunday, April 21, 2013

Light Dependent Resistors

LDRs or lightweight Dependent Resistors are terribly helpful particularly in light/dark sensor circuits. Normally the resistance of an LDR is incredibly high, typically as high as a thousand 000 ohms, however once they are illuminated with lightweight resistance drops dramatically.

The animation opposite shows that when the torch is turned on, the resistance of the LDR falls, permitting current to have it.Circuit Wizard software has been used to show, the vary of values of a ORP12, LDR .
When a light-weight level of a thousand lux (bright light) is directed towards it, the resistance is 400R (ohms).

When a light-weight level of ten lux (very low light level) is directed towards it, the resistance has risen dramatically to ten.43M (10430000 ohms).

This is an example of a light-weight sensor circuit :

When the sunshine level is low the resistance of the LDR is high. This prevents current from flowing to the bottom of the transistors. Consequently the LED doesnt lightweight. However, when lightweight shines onto the LDR its resistance falls and current flows into the bottom of the primary transistor and then the second transistor. The LED lights.

The preset resistor will be turned up or right down to increase or decrease resistance, during this means it will build the circuit additional or less sensitive.

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Bass Booster Circuit

Increase the bass output of your present instrument at modest cost!

Bass Boost is todays sound... whether its the driving, gut-vibration pulsation of disco, or the solid bass line of soft, hard, or laid-back rock. One way to get the modern bass-boost sound without running out and buying an all-new expensive piece of equipment is to use a Bass Booster between your guitar, electronic organ or what-have-you, and the instrument amplifier.

A bass booster strips the highs from the instruments output signal and amplifies low frequencies, feeding on "all-bass" sound to the instrument amplifier. Naturally, the bigger the speaker used with the amp, the more powerful the bass: use 15-inchers with the Bass Booster and you can rattle the windows. Bass Booster is powered by an ordinary 9 volt transistor radio battery. It can be assembled on a small printed board or on a veroboard using point to point wiring. The booster connects between your instrument and its amplifier through two standard RCA Jacks.

Circuit Diagram:

Bass Booster Circuit Diagram

Parts:
P1 = 50K
P2 = 100K
R1 = 22K
R2 = 470K
R3 = 47K
R4 = 10K
R5 = 470R
R6 = 1K
Q1 = 2N2222
C1 = 2.2uF-25v
C2 = 100nF-63v
C31 = 00nF-63V
C4 = 3.3uF-25v
C5 = 470uF-25v
D1 = 5mm. Red Led
Q1 = 2N2222
B1 = 9v Battery
J1 = RCA Audio Input Socket
J2 = RCA Audio Output Socket
S1 = On-Off Switch

Using Bass Booster:

Connect your electronic guitar or other electronic instrument to input jack J1; Connect output jack J2 to your instruments amplifiers normally-used input. With power switch S1 off, key S2 so the instrument feeds directly to the instrument amplifier. With P2 set full counter-clockwise (Off), turn power switch S1 on, key S2 once, and advance P2 for the desired Bass Boost level. To cut back to natural sound just stomp down on S2 and key the Bass Booster out. Dont worry about leaving power switch S1 on for several hours of a gig. The circuit pulls less than 1mA from the battery, so battery will last many, many months.

source :http://www.ecircuitslab.com

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UV Torch Light

UVrn (ultra-violet) LEDs can produce crowd pleasing effects when their gentle rnis permited to intrude with certain colours, particularly with rnreflected light underneath near-dark conditions. Also try shining some UV rnlight on a diamond.

Circuit diagram :

UV Torch Light Circuit Diagram

Mostrn UV LEDs require about three.6 V (the ‘blue’ diode voltage) to gentle. Here, arn MAX761 step-up swaping IC is used to provide constant current to biasrn the UV diode. The IC hires PWM in high-cur-rent mode and rnautomatically modifications to PFM mode in low or medium energy mode to shop tons of rn(battery) energy. To enable it for use with two AA cells, the MAX761 isrn configured in bootstrapped mode with voltage-adjustable feedback. Up torn 4 cells may be used to power the circuit however they are going to add more rnweight than you need to for a torchlight.

Torn lengthen the switch life, R1 is connected to the IC’s SHDN (shutdown) rnpin. Less than 50 nA can be measured in shutdown mode. Electrolytic rncapacitor C1 is used to decouple the circuit supply voltage. With-out rnit, ripple and noise may just cause instability. The one inductor within the rncircuit, L1, can have any value between about 10 and 50 µH. It stores rncurrent in its magnetic container whereas the MOSFET throughout the MAX761 is rnswitched. A toroid inductor is most popular on this position as it is going to rnguarantee low stray radiation. D1 must be a rather quick diode so rndon’t be tempted to make use of an 1N400x as a end result of it has a too gradual recovery rntime.

Thern circuit efficiency used to be measured at about 70%. R2, the resistor on the rnfeed-back pin of the MAX761 effectively decides the quantity of rnconstant present, I, despatched in the route of the UV LEDs, as follows: R2 = 1.5 / I

where I will doubtless be between 2 mA and 35 mA.

Zenerrn diode D4 clamps the output voltage when the weight is disconnected, whichrn may just occur when one of the vital UV LEDs breaks down. Without a load, the rnMAX761 will change L1 right up to the raise voltage and so wreck rnitself.

Author : Myo Min

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Saturday, April 13, 2013

LCD Module in 4 bit Mode

In many projects use is manufactured from alphanumeric LCDs that are pushed internally by using Hitachi’s industry-standard HD44780 controller. These displays can additionally be driven either in 4-bit or 8-bit mode. In the primary case only the excessive nibble (D4 to D7) of the display’s knowledge bus is used. The 4 unused connections still deserve some nearer consideration. The information lines can be utilized as either enters or outputs for the show. It is well known that an unloaded output is ﬁne, but that a ﬂoating high-impedance enter can result in issues. So what must you do with the four unused knowledge traces when the display is used in 4-bit mode? This question arose when a circuit used to be submitted to us where D0-D3 where tied straight away to GND (the related applies if it was to +5 V) to forestall the problem of ﬂoating inputs.

The LCD module used to be driven directly via a microcontroller, which was on a building board for checking out more than a few packages and I/O performs. There was once a switch present for turning off the permit of the display when it was oncen’t being used, however this can be forgotten during some tests. When the R/Wline of the show is permanently tied to GND (data best goes from the microcontroller to the display) then the remaining strains can safely be related to the supply (+ve or GND). In this utility then again, the R/Wline was once additionally managed by the microcontroller. When the show is initialised correctly then no longerhing much will have to go unsuitable. The information sheet for the HD44780 isn't very clear as to what happens with the low nibble all through initialisation.

Circuit diagram :
$\"LCD$

LCD Module in 4-bit Mode Circuit Diagram

After the power-on reset the display will always be in 8-bit mode. A easy test (see the accompanying circuit) unearths that it is safer to use pull-down resistors to GND for the 4 low knowledge lines. The information strains of the display are conﬁgured as outputs on this circuit (R/Wis high) and the ‘enable’ is toggled (which can nonetheless occur, even supposing it's now not the intention to keep in touch with the display). Note that in observe the RS line will even be pushed through an I/O pin, and in our circuit the R/W line as smartly. All knowledge traces become excessive and it’s not certain if (and if that is the case, for the method long) the show can survive with four shorted data strains. The moral of the story is: in 4-bit mode you should always tie D0-D3 by means of resistors to ground or sure.

http://www.ecircuitslab.com

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