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[SOLVED] NE555 as a tone generator for Morse code practice

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Larzzon:
I am quite new to the NE555 (not that i have a lot of experience at all with electronics) and thought i should learn more about it cause i know you can do bunch of stuff with it, so i found this simple circuit, see attachment.
Which is a a circuit to practice morse code which i thought would be simple enough, but i did not get the expected result.

I followed the circuit almost exactly on a breadboard, the exception i did was instead of R4 i did i put a 500Ohm resistor (also tried without the resistor). (Cause i did not have an 1KPot at home).

The result i was expecting was a good tone from the speaker (frequency depending on the resistance over R10 100KPot), but i only get an extremely weak tone (barely possible to hear) when "pressing" the key (the key is just to loose wires) (with R4 at 0 Ohm) but i clearly can hear the speaker "click". And if i would get the tone at the same volume as the click i would be happy.

I hope that someone can explain to me why i did not get the results i expected.

I did not buy the kit, just found the circuit online and realized i had everything at home to make it, except the 1KPot.

And i shall mention that i have tried two different but similar circuits and got the same not expected results.

Best regards

Stefan



AvariCe:
Hey Stefan, my guess is that the 555 timer can't pass enough current to the speaker.
If you have an NPN transistor, try the circuit on the left.

Edit: removed malicious link.

ledtester:
Some questions and things to try:

0. Is your 9V battery fresh? Or are you using a power supply?

1. Try removing R4 entirely - just connect that one end of the speaker directly to C3.

2. Can you post a picture of your set up including the speaker?

3. Do you have a piezo disk like this:



It might work as a better speaker. You can find them in magnetic window/door alarms which are cheaply available:



4. What test equipment do you have? Scope? Frequency counter? Multimeter? If you have a multimeter, what model is it?

5. When powered the circuit should be switching the output (pin 3) from +9 to 0 very quickly. You can check this with a LED as follows:

Replace C3, R4 and the speaker with a resistor and an LED:

--- Code: ---          pin 3 ---- /\/\/\/ ---- LED ---- GND

--- End code ---
The resistor can be anything >300 ohms. It won't matter which way you plug in the LED because you'll be testing it in both orientations. In both orientations the LED it should light up (constantly). This will verify that the 555 is oscillating. If you have a frequency counter mode on your multimeter you can determine the frequency of oscillation - just put one probe on pin 3 and the other on GND.

Larzzon:

--- Quote from: AvariCe on September 15, 2019, 03:12:25 pm ---Hey Stefan, my guess is that the 555 timer can't pass enough current to the speaker.
If you have an NPN transistor, try the circuit on the left from here.

--- End quote ---

I can't enter the website which you are linking, cause my firewall in my router is blocking it, and my browser is saying that it is not safe, and my antivirus/firewall is warning me.


--- Quote from: ledtester on September 15, 2019, 03:25:06 pm ---Some questions and things to try:

0. Is your 9V battery fresh? Or are you using a power supply?
  I am using a powersupply.

1. Try removing R4 entirely - just connect that one end of the speaker directly to C3.
It gets a bit louder without R4 but the "click" is still a lot louder than the tone, the tone is barely possible to hear.

2. Can you post a picture of your set up including the speaker?
  (Attachment Link)

3. Do you have a piezo disk like this:

I am pretty sure my speaker is not a piezo element, the speaker is magnetic if that says anything. (and it looks like an ordinary speaker element.), altough i might go shopping for a piezo element tomorrow, i am curios to see if it is the speaker

It might work as a better speaker. You can find them in magnetic window/door alarms which are cheaply available:

4. What test equipment do you have? Scope? Frequency counter? Multimeter? If you have a multimeter, what model is it?
I do have an DSO138, haven't really figured it out yet (i gave it a try but did not manage to get anything i could use), But as i said in my post i do hear a tone and i can notice a change when adjusting R3. Yes i do have an cheap multimeter but it can't measure frequency.

5. When powered the circuit should be switching the output (pin 3) from +9 to 0 very quickly. You can check this with a LED as follows:

It lit when connected "correctly" with the anode connected to pin 3. But not the other way around, although the only led i had was L-7104ID-5V, which has an built in resistor if that would change anything, so i did not use a separate resistor, at first, then i tried with 510Ohm when anode to gnd),

Replace C3, R4 and the speaker with a resistor and an LED:

--- Code: ---          pin 3 ---- /\/\/\/ ---- LED ---- GND

--- End code ---
The resistor can be anything >300 ohms. It won't matter which way you plug in the LED because you'll be testing it in both orientations. In both orientations the LED it should light up (constantly). This will verify that the 555 is oscillating. If you have a frequency counter mode on your multimeter you can determine the frequency of oscillation - just put one probe on pin 3 and the other on GND.



--- End quote ---

AvariCe:

--- Quote from: Larzzon on September 15, 2019, 05:37:12 pm ---
--- Quote from: AvariCe on September 15, 2019, 03:12:25 pm ---Hey Stefan, my guess is that the 555 timer can't pass enough current to the speaker.
If you have an NPN transistor, try the circuit on the left from here.

--- End quote ---

I can't enter the website which you are linking, cause my firewall in my router is blocking it, and my browser is saying that it is not safe, and my antivirus/firewall is warning me.


--- End quote ---
Sorry, due to my setup everything was blocked and didn't notice the page had a crypto miner. Anyway, I attached the schematic.

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