little prototype - beginner in electronics needs advice from the gurus! -Timer application

Thread Starter

joulini

Joined Nov 28, 2017
2
hey folks!
i want to build a little prototype which does the following:

1) count up to 1 or 2 hours
2) sound a simple tone from a piezo
3) can then be switched of by a button and
4) starts from 1) again.

it should be:

1) as small as possible (with non expensive standard components)
2) therefor powered by a little battery cell

now i tried to research as much as possible about these topics and came to the maybe wrong conclusions that it must have some kind of microcontroller like the 555 or the pic PIC10F200 or any of its kind which is able to do a PWM. But then im a very much stuck on the details, because there seem to be many different versions of each of this MCUs and its hard for me to figure out how to build the circuit and which pins i need on the MCUs and which i dont.

If somebody could point me to the right directions of which MCUs are best suited for a task like this and generally where to start to get this circuit going it would help me a great deal and would me mucho appreciated!

Im sorry for being so general about me request and for my foreigners english.

cheers and thanks very much in advance,
julian
 

MrChips

Joined Oct 2, 2009
21,051
Welcome to AAC!

The cheapest, simplest, and lowest part count solution is using an MCU.

You do not need PWM. Any low end MCU of recent vintage will work. It will work off a 3V CR2032 button cell and can run for years without needing to change the battery.

555 is not an MCU.
 

DickCappels

Joined Aug 21, 2008
6,374
Your English is just fine.

The PIC10F200 would be ideal if you are able to use timer interrupts to generate pulse width modulation.

Otherwise you might want to consider the CD4060 or the HEF4541B as good ways to generate long time delays reliably. (The NE555/LMC555 are not very easy to use for time delays greater than a minute or two.)
 

Thread Starter

joulini

Joined Nov 28, 2017
2
hi again folks!

thanks alot for the input and advice, its much appreciated!

im wondering if there would also be a way to do this project without an MCU and use just a timer like the 555 instead?
what i learned from reading through some articles (and again im most probably wrong :) ) is that its hard to achieve longer timing periods than milliseconds or a second with these timers.

my point is if i would be able to save me the time of learning to program MCUs i would consider goint that way as well. the timing doesnt have to be super preciese as well.

maybe you have some houghts on that?

and if a MCU is obligatory, are there ones with a more newby friendly approach in terms of programming and general complexity fo operation which you could recommend?

many many thanks in advance again for any wink in the right direction!!

wish you all a nice day,
julian
 

btondin

Joined Apr 27, 2013
7
I would do that using a low power, low voltage MCU like the PIC12F1822 that you wouldn't need a LDO. You can put the PIC to sleep with watchdog timer consuming something like 1uA and wakeup every 16 seconds, increment a variable and when it reaches 225 (1 hour) you can sound the piezo. Set your internal clock for less than 1MHz and the battery will last "for ever".
 

Colin55

Joined Aug 27, 2015
519
In my project above, the longer you keep the circuit turned ON, the longer the battery lasts because the circuit charges the battery and it is guaranteed for 35 years.
I have to keep replacing the full batteries with old ones because the are fully charged.
 

Colin55

Joined Aug 27, 2015
519
Here's a simpler circuit:
LONG DURATION TIMER
To get a long duration timer we can create an oscillator, called a CLOCK OSCILLATOR, and feed it to a number of flip-flops. A flip-flop is a form of bi-stable multivibrator, wired so an input signal will change the output on every second cycle. In other words it divides (halves) the input signal. When two of these are connected in a "chain" the input signal divides by 4. The CD4060 IC has 14 stages. These are also called BINARY DIVIDERS and the chip is also called a COUNTER.
The IC also has components (called gates or inverters) on pins 9,10 and 11 that can be wired to produce an oscillator. Three external components are needed to produce the duration of the oscillations. In other words the frequency of the "clock signal."
The output of the oscillator is connected (inside the chip) to the Binary Dividers and each stage goes HIGH then LOW due to the signal it is receiving. Each stage rises and falls at a rate that is half the previous stage and the final stage provides the long time delay as it takes 213 clock cycles before going HIGH. We have only taken from Q10 in this circuit and the outline of the chip has been provided in the circuit so different outputs can be used to produce different timings.
The diode on the output "jams" the oscillator and stops it operating so the relay stays active when the time has expired.
upload_2017-12-4_13-15-34.gif

 

Wendy

Joined Mar 24, 2008
22,141
That relay will suck battery life, I have designed similar circuit where a relay is not used (also using the 4060) qty2 4060ICs can make a wide range of timing durations The 4060 is a neat chip, It also has a Resistor Capacitor oscillator built in that will allow a wide range of custom designs

In my project above, the longer you keep the circuit turned ON, the longer the battery lasts because the circuit charges the battery and it is guaranteed for 35 years.
I have to keep replacing the full batteries with old ones because the are fully charged.
Say what? Where is the electrical energy coming from?

If you used a sonalert instead of a piezo speaker it would simplify your design quite a bit.
 
Last edited:

Colin55

Joined Aug 27, 2015
519
"If you used a son-alert instead of a piezo speaker"

It is a son-alert. My son is alert to the fact that it has its own inbuilt driver and now costs a staggering 8 cents on eBay.
 

Colin55

Joined Aug 27, 2015
519
"The 4060 is a neat chip, It also has a Resistor Capacitor oscillator built in"

You must have the new 4060 chip from "Shonks Incorporated" that has inbuilt microcontroller, TFT display and 15 watt solar panel, all for 32cents including overnight courier delivery.
 

Colin55

Joined Aug 27, 2015
519
"Set your internal clock for less than 1MHz and the battery will last "for ever".'

I made his circuit and lowered to clock and the battery started to charge.
 
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