Hi
I tried this circuit and would not work

Have a 40 watt 4 ohm speaker or a 1 watt 8 ohm speaker

Tried 10k resistor and 100k resistor
With a 9 volt battery

Thanks

 

Without the speaker connected, does it flash the LED?

 

Without the discharge pin connected, how is the timing capacitor supposed to get discharged?

Look at the 555 datasheet and try to use a proper circuit.

Also, consider whether expecting a 555 output to directly drive a low-impedance speaker is realistic. I haven't done much with speakers, so maybe it is reasonable to get some decent sound directly.

 

Without the discharge pin connected, how is the timing capacitor supposed to get discharged?

by the Output pin.

 

Hello,

@WBahn , The circuit uses pin 3 ,the output, for charging and discharging the capacitor.

Bertus

 

by the Output pin.

Ah, yes. Old eyes playing tricks on me. I thought I was seeing something that wasn't there. Thanks.

But that would seem to underscore the concern about whether the output can really pull the low-impedance load low enough.

 

The NE555 can source or sink 200mA. 200mA would be 320mW into 8Ω so it should produce audible sound.
But it MUST be an NE555, not a CMOS version with different letters at the start.

 

A 47k timing resistor and 10uf capacitor gives a run frequency in the order of 10Hz, which is to low to hear in the speaker and too fast to see the led flashing.

With a 47k resistor, 10n cap should generate an audible tone, or a 100uf cap should blink the light visibly.

 

A 47k timing resistor and 10uf capacitor gives a run frequency in the order of 10Hz,

For the circuit shown I make the frequency around 2Hz which would give clicks in the speaker and a flashing LED.
f = 1/ (1.4 * RC)

 

A 47k timing resistor and 10uf capacitor gives a run frequency in the order of 10Hz, which is to low to hear in the speaker and too fast to see the led flashing.

It's not a sinewave! You would hear 20 clicks per second - a bit of a buzz.

 

For the circuit shown I make the frequency around 2Hz....

I just took a quick look at the datasheet chart. I was within an order of magnitude!