Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
@ljcox: Regarding the tone oscillator in the latest drawing, you wrote "Set tone 1 with Rb c3, Tone 2 with (Ra+Rb)C3" Just for clarification, the two tones I want are G# and E (for High and Low, respectively). Using the resistor values I posted for the notes in Post #24, that would be G#: 15 K...
Thank you very much! I'll get started on assembling that tomorrow after I pick up a couple resistors and capacitors for it. I'll let you know how I make out with it.
You bring up a good point about a person lingering in the doorway. As the dining area of this sandwich shop is limited and it's not uncommon for them to have a line up at lunch time, it's possible that the line extends out the door and a person could continuously trigger the circuit.
@ljcox...
Much of what you said doesn't make sense to me. I'm afraid I'm not very knowledgeable to know what FPGA is, other than to Google it and Field-Programmable Gate Array sounds much more complicated than what I'm looking for. In any case, my original need of a 'short beep circuit' has changed during...
I have no PNP transistors, but I can easily pick some up as well.
If I was starting this from the beginning, I would probably use a PIC as well, from what I've briefly read about them. I'm not sure where I would even start with something like that.
My apologies, I prefer the first option, with the volume fading after the 1 second tone. It can be a fairly quick fade, too. Just something to smooth out the end of it.
My wall wart outputs 12v, so I can use that for the amplifier.
Which would be preferable, the TDA 1905 or LM380? And...
I'll check with my supplier tomorrow for the ZL-3600, or other audio amp IC. It's too bad they don't have their inventory online so I could plan out what I want to buy.
You're correct, I'd want the second tone to decay in volume, so it has a natural fade sound to it like a bell. It's not a big...
I have very good news to report! The circuit works fabulously!
Now for the final touches:
If I understand it right, if I want to shorten the length of the first tone, after the sensor goes low, I can use a smaller resistor for R1. And to shorten the length of the second tone, that would be...
So .. basically, the pot to + Input. The Sensor, through the noise filter and the 10K for the hysteresis to the - Input. In effect, just swapping the inputs to get the inverted logic?
I did that and the circuit works invertedly (is that a word? haha). The high note is on constant, I put my hand...
I found the manual for my meter online. It has >10 Mohm Input impedance, and the fuses check out good.
I also figured out how to switch from AC A to DC A .. it was a button that the label was worn off (my meter was given to me used), and I had to switch the red probe to another socket.
1. I...
In case I wasn't clear earlier, putting the probe on A doesn't keep A low. If I have the probe on A (even without the other probe grounded), it makes the circuit work properly. Without it, I put my hand over the sensor and I get the high note (IC2d). Remove my hand and it goes silent. I'm not...
The Arduino Uno is an open source, open hardware microcontroller. It has analog input/outputs, digital input/outputs, etc. You write the program using a simplified C++ language and upload it to the board, then it runs the software. The simplest program would make an LED blink. For many projects...
I finally have some good news to report. Or at least some advancing in a forwardly direction :)
I don't have a copy of the circuit in the sensor, just the block diagram from the datasheet (see link below).
I thought that the feedback must have been coming from the sensor. My loving wife bought...
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
