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Topic: Need help: Arduino + 555 timer + loud alarm signal (Read 336 times) previous topic - next topic

alexmg2

This is the piezo I am using, if I connect it directly to arduino it works just fine.
https://www.adafruit.com/products/1739

I tried two different transistors already, same result.
I did forget to mention that I am running arduino off USB is that makes any difference.

I will take a dinner break, then will rewire everything and will record its function and post here for troubleshootign.

Thanks.

raschemmel

#16
Apr 22, 2016, 06:13 am Last Edit: Apr 22, 2016, 06:49 am by raschemmel
Post a photo of your circuit. That kind of piezo is never very loud but it should be working. Are you SURE the base resistor is 1 k ? Try changing it to 150  to 220 ohms.
Did you do what I said about putting a jumper wire from the anode of the diode to GND to test it ?
Something is definitely not right. That's a simple circuit. It should have worked from the start.

Measure the voltage on the base of the transistor when you connect the base resistor to +5V.
Measure the voltage on the collector too.

Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

alexmg2

Nope, still the same result, I triple checked the circuit, ran it from both , USB and Wall power, two different resistor values, 1k and 150R there is a tiny bit difference with 150R it is louder comparing to 1k, but still waaaay quieter than if I connect piezo directly to arduino, my program is simple. It generates frequency via timer interrupt. tone command also gives the same result. Standard test "Melody" program from arduino package - same quiet result.
Here are two videos:

This is straight from arduino, pin8 and GND
https://www.dropbox.com/s/s3le5bjm2oekp0a/Video%20Apr%2022%2C%2012%2044%2026%20AM.mov?dl=0

And this is via transistor
https://www.dropbox.com/s/h1o6xpmlh6lspfo/Video%20Apr%2022%2C%2012%2053%2002%20AM.mov?dl=0

raschemmel

#18
Apr 22, 2016, 01:28 pm Last Edit: Apr 22, 2016, 01:31 pm by raschemmel
I find that hard to believe. I can't see your circuit in the video . Can you post a closeup (from directly above) photo of your circuit ? it is possible this problem is due to the fact that the piezo draws such little current. I can tell you that my transistor circuit with a 2 " , 8 ohm speaker was louder than your piezo.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

alexmg2

I will reassemble this circuit on naked arduino when I get home later tonight and will fire it up again.  Yeah, I cannot beleive this either, it seem such simple and bulletproof schematic.

raschemmel

Have you tested the transistors using a led and a resistor instead of the piezo ?
Have you tried the Blink example to drive the piezo to ruleout software issues ?
Have you tried ohming out transistors using a DMM on diode scale with the black lead on the base and the red lead on emitter and then collector ?

You should find that on diode scale , there is a SLIGHT difference in the reading between collector and base vs emitter and base (with the black lead on the base).

Test the transistors using the Blink example.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

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