Running Lights with CD4017

 555-Circuits, Digital-Circuits, LED-Circuits  No Responses »
Oct 292004
 
Running Lights with CD4017

The 555 Astable generates a clock for this circuit, an oscillator giving a square wave output at pin 3 which is counted by 4017 to give a running lights effect. The decade counter-divider CD4017 has 10 outputs, for every low to high transition at the clock input, rising edge, the counter advances one LED. After going one full circle the the first LED lights again and it goes on. You can vary the value of R2 100K Linear potentiometer to make LEDs run fast or slow. The frequency of oscillation of astable 555 is given as f = 1.44 / Read More …

 Posted by admin at 11:27 AM

Drive SCR thyristor with 555

 555-Circuits, Power-Supplies  No Responses »
Oct 232004
 
Drive SCR thyristor with 555

This circuit gives a burst of pulses to fire 2 SCRs, when pin 4 is taken to 12V the SCR is turned on, to use this circuit you need 12V short pulses phase shifted with respect to AC sine wave on bridge, like this you can control the bridge from near 0% to near 100% ON, That way battery banks can be charged, electroplating can be done, current and voltage can be controlled with opamps, thyristors are very rugged compared to transistors and MOSFETS in that order. Edit the circuit eagle cad file del00015.zip, eagle cad has a free version Read More …

 Posted by admin at 12:31 PM  Tagged with:

OR gate with two 555

 555-Circuits, Digital-Circuits  No Responses »
Oct 232004
 
OR gate with two 555

This shows how to OR gate two 555, when one 555 cycles at a low frequency a valve turns on an off, the second 555 stretches the ON duration of the pulse with a diode OR gate. The OR output uses sample and hold to get the stable analog data from a sensor after the actuator has gone OFF, this ensures correct reading. 555 is a fundamental Mixed Signal Circuit as it can be made into a VCO using Pin-5. If you see old exar databooks, you can see 555 and PLL and Tone decoders all applications compiled in one Read More …

 Posted by admin at 12:30 PM

555 watchdog for uC and uP systems

 555-Circuits, Embedded-Systems  No Responses »
Oct 232004
 
555 watchdog for uC and uP systems

When the microcontroller hangs due to a spike, EMI or RFI etc. the 7555 will reset the uC, if proper power supply design is done above circuit can also give a clean power on reset, the above circuit you should modify to suit your design. Better still use a uC with watchdog built in like some atmel chips, or use the watchdog chips from maxim which can also do RAM battery management. The circuit was developed over a old TI application note, 7555 i think fairchild may be making it, 7555 is CMOS version of 555 timer, advantage of 7555 Read More …

 Posted by admin at 12:28 PM

Fixed frequency Variable duty cycle with 555

 555-Circuits, Mixed-Circuits  No Responses »
Oct 232004
 
Fixed frequency Variable duty cycle with 555

This circuit is based on a very old application note from exar, in this the frequency is fixed by IC1 and IC2 -P1 controls the duty cycle. you need to compute the R and C values to get what you need, LM555 data sheet. You have to study the circuit and do something more innovative perhaps, just copying is ok for learning but it will get you nowhere, so learn and then innovate, the eagle circuit is given below so you can learn by editing it, also design a PCB with it, and you can even make a PCB at Read More …

 Posted by admin at 12:28 PM  Tagged with:

Pulse width modulation using 555

 555-Circuits, Power-Supplies  1 Response »
Oct 232004
 
Pulse width modulation using 555

IC1 astable gives a fixed square wave at pin 3, C1 and R1 derive uS trigger pulses from IC1 and this will trigger IC2 monostable or single shot, the voltage at pin 5 of IC2 will change the pulse width output of IC2, to get it working all the three RC combinations have to be figured out. You can even build a small SMPS with this or even control the temperature of your soldering iron using the SSR solid state relay circuits in power section, then you need to think and design the cycle time of a soldering iron heat Read More …

 Posted by admin at 12:25 PM
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