Hello everybody. I’ve been lurking around the forums here for quite a while, trying to find a timer design that I can make on my own. Unfortunately, my background isn’t in electronics, but I do understand basic theory and assembly techniques.

The timer is actually just a piece of the larger project, which is a battery charger/discharger unit to test battery capacity.

Is anyone interested in helping me out? The timer I have in mind is a count up from 0 to 20 minutes and then a buzzer sounds, two digit seven segment display to show minutes elapsed, with start and reset buttons.

This is a very simple design for a lot of you guys here. I would really appreciate a hand with this. The whole idea behind the project is to make a tool that I can use at my job.

Thanks guys for any help offered! I might be able to get a free helicopter ride to whoever can help me finish this project. (in NC)

 

Any experience with Arduino or any type of programming ?

I will look at an approach that uses a simple board, with a micro, but possibility no
code has to be written. Once I do the eval I will post feasibility.


Regards, Dana.

 

Hi Dana.

Any experience with Arduino or any type of programming ?

No, I haven’t even looked into Arduino. I know it’s a higher technology and probably easier to put together, but I do enjoy soldering components onto circuit boards. The more hands-on a project is, the more relaxing and enjoyable I find it to be.

I was thinking possibly using 555 chips, POT for timing, a couple of old-school LED’s for an elapsed time display, maybe a buzzer to indicate the 20 minute time has elapsed. I think the LED display might need a chip to power it as well. This is as far as my knowledge takes me. I’m hoping to learn a ton from this project.

Thanks for the help!

 

I believe you are going to find there are several ways to do what you wish to do. You can use a micro controller as danadak mentions above or just build a countdown times using discreet components. Each method has it's good and bad points. Using a micro-controller within itself has several options as does using discreet components.

The timer I have in mind is a count up from 0 to 20 minutes and then a buzzer sounds, two digit seven segment display to show minutes elapsed, with start and reset buttons.

Not to dissuade your thinking here but I would be thinking a Count Down timer rather than Count Up timer. Using discreet components there are dozens of decade counter circuits out there to choose from. Most involve "cascading" a few chips like the 74192 counter (or similar). Yes, using the 555 timer you mentioned you could build a 1 Second clock to drive a decade divider chip. A Google of 74192 or 74193 Counter Circuits will bring up dozens of hits. I see you posted since I began typing. Well if you like bread boarding and soldering using discreet components will afford you plenty of that. I only mention the 74192 and 74193 as a few possibles, there are dozens of other counter / timer chips available.

The merit to using a micro-controller like an Arduino is there are hundreds of code samples online which can be used and a single micro-controller with a small liquid crystal display will really reduce the parts count and complexity of assembly.

So depending on what you wish to learn those are a few options.

Ron

 

There are quite a few ways to approach this.

One is discrete logic, like this -

https://forum.allaboutcircuits.com/search/3189/?q=up+down+2+digit&o=relevance

https://forum.allaboutcircuits.com/attachments/up_down-2-digit-7-seg-counter-circuit-pdf.31220/

https://www.electronics-tutorials.ws/counter/bcd-counter-circuit.html


Search the web for "two decade LED counter DIY" or some variant like that.



Another is combination of Arduino and driver logic. Program Arduino thru block programming.
Block programming is drag and drop blocks into a gui window, config them, then tool converts
that to Arduino code and programs the Arduino. Scratch for Arduino would be a good starting
point. http://s4a.cat/ is website There are some videos there to give you a feel.

Start simple, blink an LED.

Arduino would handle the button command presses and counting, and then output that to a driver
chip for the LED. As well as do the test for 20 mins and generate the buzzer sound.

This is not a quick way, learning is involved, but its not too bad doing it with block programming.



Regards, Dana.

 

Simple Arduino + an I2C driver like https://www.adafruit.com/product/879

Maybe use ATTINY85 -

\

The above a different application but a rough view of the ATTINY85, it would feed the I2C driver with
just two pins.

or https://datasheets.maximintegrated.com/en/ds/MAX6955.pdf


Regards, Dana.