There its wrong as you said but check how it is working in this video. you can witness how its soldered at YouTube >The schematic is wrong, the left 555 timer's output pin 3 should be going to the BD139, not pin 2+6.
2SD882 is fine for a substitute, this is only a 5V siren. Best to have a diode or snubber across the speaker if you want more power like at 12V operation.
Take a look where the 1k resistor goes, in the built circuit. It's to pin 3. The two control voltage diodes are also opposing.There its wrong as you said but check how it is working in this video. you can witness how its soldered at YouTube >
I made this back in 1978 when it was all the rage to have a "Kojak" siren in your car, i used a push pull output ..Indeed, that is what the LM386 is for... A simple addition.
An "Americanized" version... Plenty to choose from on Google...
View attachment 207185
I would also note the there are several "siren" IC dip chips manufactured. One in particular has the US used 4 tones (police/ambulance/fire) plus a flipflop for the flasing lights bar all on one chip.
Thanks very big brother! the 1N4007 WITH 1K Resistor was upside down in the circuit as well..Why are most electronics videos on You Tube from India now? I could not understand what he was saying. The tiny speaker has a very high pitch (a squeaker).
The schematic is wrong, the output is a squarewave from pin 3 of the 555, not a triangle wave from pin 2 which would prevent oscillation. The frequency sweep is caused my modulating the DC voltage on pin 5 as shown in the datasheet.
|Thread starter||Similar threads||Forum||Replies||Date|
|Help with using a PIR to trigger a NE555||General Electronics Chat||124|
|A||VCO with op amp and NE555||Homework Help||3|
|I||ne555 capacitor type||General Electronics Chat||4|
|How do I make ne555 work only once?||Analog & Mixed-Signal Design||18|
|T||NE555 burning issues||General Electronics Chat||5|
by Gary Elinoff
by Jake Hertz
by Gary Elinoff