Mains Current Indicator with a LED

 Discrete-Circuits, LED-Circuits, Mains-Power  No Responses »
Nov 302004
 

This is a mains 230V AC load current indicator and is a LIVE CIRCUIT, so take care. The Resistors have to be a fusible ceramic wire wound.

This circuit has been drawn from my memory and i have not tried it out again, just see if it is ok and then try. You should use the fuse of 1A a slow blow if you want but it is very important. You can design the shunt R3 and Fuse rating as required by your load. Note that this circuit is to be put in series with the load like an ammeter. If you put it across the supply like a voltmeter it will fuse out or burn out. This circuit has to be enclosed in a plastic sealed enclosure to avoid contact.

Mains Current LED Indicator

 Posted by admin at 2:47 AM

Mains Voltage Indicator with a LED

 Discrete-Circuits, LED-Circuits, Mains-Power  No Responses »
Nov 302004
 
Mains Voltage Indicator with a LED

This is a mains 230V AC voltage indicator and is a LIVE CIRCUIT, so take care. The Resistor has to be a fusible ceramic wire wound and the capacitor 630V AC or higher capacity. This circuit has been drawn from my memory and i have not tried it out again, just see if it is ok and then try. You should use the fuse of 100mA a slow blow if you want but it is very important. This circuit has to be enclosed in a plastic sealed enclosure to avoid contact.

 Posted by admin at 2:46 AM

Monostable Multivibrator CD4538

 Digital-Circuits, Mixed-Circuits  No Responses »
Nov 082004
 
Monostable Multivibrator CD4538

CD4538 is a dual Monostable Multivibrator. When you trigger the chip the output sends off one single pulse or one high-low event. The T+ pin 4 of U1a is the positive edge trigger or raising edge trigger input, the T- pin 5 is falling edge or negative edge trigger input. Now see the image of the single pulse above which shows both the edges, If this is the input pulse at pin 5 then the falling edge turns the output pin 6 from low to high, this output remains high for time T = R2 * C1 and then goes Read More …

 Posted by admin at 10:24 PM

Digital to Analog with R2R Ladder Network

 Mixed-Circuits, Test-Measurement  No Responses »
Nov 082004
 
Digital to Analog with R2R Ladder Network

This is a R-2R Digital to Analog Converter, It converts a byte (8 bit) to a analog value. It has 256 levels including zero. This can be used to convert a byte sent from a microcontroller to a analog value like say 1.51 V. At full scale, when all 8 bits are high calibrate to give 2.55 V then ever bit increment is 0.01V, 10mV steps. If the eight bits inputs are from a counter you then will see a staircase waveform at output, each step being 10mV higher or lower depending on whether the counter is counting up or Read More …

 Posted by admin at 10:23 PM

LM311 Square Triangle Oscillator for PWM

 Mixed-Circuits  No Responses »
Nov 082004
 
LM311 Square Triangle Oscillator for PWM

LM311 is a comparator, It operates from single 5V supply or dual supplies,input current 150 nA, 50 V-50 mA output drive capability. TTL-CMOS compatible output. The Output is open collector so it can sink current but cannot source, a totem pole output can source and sink. In this Circuit R2 is the source or pull-up. The Output being high or low depends on which input is more dominant or positive. If + or non-inverting input is more positive than the – inverting input then output of LM311 is high impedance or high Z as output transistor of LM311 is turned Read More …

 Posted by admin at 1:01 AM  Tagged with:

Frequency Divider 74HCT4040

 555-Circuits, Digital-Circuits  No Responses »
Nov 062004
 
Frequency Divider 74HCT4040

U1 7555 is a CMOS version of 555. The 555 here is in Astable Oscillator mode, C1 and C4 are decoupling capacitors 0.1uF value, ceramic disc. The output is around 100kHz, If C3 is plastic or mica the frequency output will be stable with temperature. It is better to use a crystal oscillator. The 555 output is fed to clock input of 4040, the output of 555 will be a square wave, on every high to low transition (falling edge or negative transition) the counter increments by one and the output is 12 bit binary. If input frequency is F Read More …

 Posted by admin at 5:15 AM

Crystal Oscillator – Parallel Resonant

 Digital-Circuits, Embedded-Systems  No Responses »
Nov 062004
 
Crystal Oscillator - Parallel Resonant

74HCU04 is a chip that was made for this purpose, HCT may not work for such a circuit. C1 and C2 can go to upto 33pF and R2 can be increased to make R2 * C2 = t. Time constant much less than the period T of the crystal T = 1/F . This is to remove higher frequency components in the Oscillator. The circuit above is a parallel resonant oscillator circuit. The Crystal works by the piezoelectric principle, piezo means pressure. The electric field causes the impedance of the crystal to change. The LP Record Player needle is the Read More …

 Posted by admin at 5:15 AM  Tagged with:
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