How this circuit works

[fugrammer]

hi, this is a circuit that changes the color of the LED.First, LED1 is red and LED2 is green, then LED1 is green and LED2, and this process continues. Can someone explaine to me how it works? thks.

 

[Hero999]

It's essentially the same as an astable multivibrator.
https://en.wikipedia.org/wiki/Astable_multivibrator#Astable_Multivibrator_circuit

 

[Nigel Goodwin]

It's not the 'same', it IS an astable multivibrator - it's just drawn upside down.

 

[Clyd3]

yssid gnileef si i
it's amazing how often we miss things on circuit diagrams because of their orientation

 

[muki55]

It's not the 'same', it IS an astable multivibrator - it's just drawn upside down.

I agree with hero999.

 

[Nigel Goodwin]

I agree with hero999.

Why would that be?.

 

[Gayan Soyza]

Bro fugrammer i saw ur cct.it just a astable multivibrator.only change it uses two pnp transistors.
according to my specifications it changes the colours from first (led1 red, led2 red) secondly (led1 green,led2 green).not like u describe (led1 red,led 2 green) secondly (led2 green & led1 )

bye

 

[fingaz]

This certainly is an Astable Miltivibrator. (Aka free-running multivibrator) because it cannot rest in one state, it constantly alters. As the capacitors charge and dis-charge, they alter the state of the transistors (ie. switch them on and off) which controls which of the led's is lit. It's basically a flip flop that triggers itself constantly.
hope this explains how it works.

 

[Roff]

The beta of those transistors would need to be well over 200 if you want the period of oscillation to be predictable and stable. Also, base-emitter breakdown will make the period unpredictable, and can cause beta degradation.
I would add a general-purpose diode between +9V and the junction of the two emitters (anode to +9V), lower the values of R3 and R4 to 10k each, and change C1 and C2 to 100uF each.
As a side note, has anyone ever seen a radio that is safe to drink?

 

[Hero999]

Why would that be?.

Well I agree with you (I know my wording wasn't very good in previous post). Therefore he therefore agrees with you.

 

[JimB]

As a side note, has anyone ever seen a radio that is safe to drink?

A rather unfortunate lack of proof-reading.

JimB

 

[fingaz]

A rather unfortunate lack of proof-reading.

JimB

just shows that a slight typo can alter the meaning of the sentence enormously

 

[eblc1388]

Bro fugrammer i saw ur cct.it just a astable multivibrator.only change it uses two pnp transistors.
according to my specifications it changes the colours from first (led1 red, led2 red) secondly (led1 green,led2 green).not like u describe (led1 red,led 2 green) secondly (led2 green & led1 )

You've made my day.

 

[Roff]

Bro fugrammer i saw ur cct.it just a astable multivibrator.only change it uses two pnp transistors.
according to my specifications it changes the colours from first (led1 red, led2 red) secondly (led1 green,led2 green).not like u describe (led1 red,led 2 green) secondly (led2 green & led1 )

bye

Your specifications are ignoring the polarity dots on the bicolor LEDs.

 

[opomulero]

hello sir,
i am not wriitng to reply your post but am now writing to request for your help on lcd thermometer, the schematic diagram but the one that doesnt require programing. I WANTED to do this for my final year project in school and if you have any other project you will like to give me so that i can do it as final year project, i will gladly appreciate it.
Thanks
opeyemi ojo
opeyemiojo12@yahoo.com

 

[opomulero]

Help On Lcd Thermometer

hello sir,
i am not wriitng to reply your post but am now writing to request for your help on lcd thermometer, the schematic diagram but the one that doesnt require programing. I WANTED to do this for my final year project in school and if you have any other project you will like to give me so that i can do it as final year project, i will gladly appreciate it.
Thanks
opeyemi ojo
opeyemiojo12@yahoo.com