Max (resistor/capacitor) values for 555 timer monostable circuit ?

danadak

Joined Mar 10, 2018
4,057
The object sensor output is open collector transistor .

i used 470 uf with 12v , i got 7 min period :)

sorry guys, i forgot to till you while the object still crossing the sensor the lamp should be on :(
and this cant achieve with iimagine circuit and i dont know if i can do that using 555 timer :rolleyes:


could you advice me to use microcontroller to do what i need? :rolleyes:


Regards

mBlock visual programming language and an Arduino Nano, Uno, even an 8
pin ATTINY85 would do, ~ 2% accurate timing.

Here is what i think are your basic requirements done in mBlock.

You drag / drop blocks, config, and the tool generates and uploads the Arduino "C" code.

upload_2019-8-11_20-0-32.png

The code it generates for you looks like this -

upload_2019-8-11_20-3-10.png

All you need is board, maybe an R in series with light sensor to make a voltage
divider to feed to the UP A/D pin and of course power.

If you use boards that have onboard xtal timing accuracy will be << 1%,
if ATTINY85 ~ 2%


Regards, Dana.
 
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danadak

Joined Mar 10, 2018
4,057
Using Nano looks like -

upload_2019-8-12_5-29-54.png

The photo trans R sets the output V into Arduino A/D, so you tailor for the part
you are using.

Power either USB from a small brick, or external. Board has regulator on it.

To use ATTINY85 instead of Nano slightly more complicated. Actual programming
of ATTINY can be done with a Nano or Uno board, you first config those boards as
"Arduino as ISP", then take code from mBlock paste into Arduino project, compile
and program. a little more involved.

With ATTINY85 or Arduino in general should be no output glitches on power
up.


Regards, Dana.
 
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iimagine

Joined Dec 20, 2010
483
sorry guys, i forgot to till you while the object still crossing the sensor the lamp should be on :(
and this cant achieve with iimagine circuit
Even better! no idle current wasted.
DeleteMe.PNG
Since you mentioned your sensor is an open collector type:
The circuit on the left will do, but wasting a bit of power every time the object moves; could use a darlington style and reduces bias current consumptions.
The circuit on the right uses a P-Mosfet which consumes practically no current if you make that pull up resistor 10M.
Everytime the sensor senses a movement, it draws current (open collector), thus turn on the bjt / P-Mos which keeps the capacitor fully charged mean while the N_Mos conducts and turn on the lamp. The N-Mos remains on, uninterrupted till the capacitor is discharged via the 10M resistor (or 1M).
RL value depends on the supply voltage and bjt/p-mos max current draw capacity so that it wont burned up
 

MrAl

Joined Jun 17, 2014
8,119
You can also use two 555's in tandem to get a longer delay with smaller caps.

I've used 100uf with one older style 555 and i had a problem with it because the 555 could not discharge it properly.
I put a small value resistor in series with the cap and then the circuit worked ok
However, trying another 555 package it worked ok without the extra resistor.

I've used the counter idea discussed elsewhere in this thread and it works good. You have to have a way to stop the oscillator though or maybe disable the counters, something like that, to get it to stop timing.
 

danadak

Joined Mar 10, 2018
4,057
The ATTINY solution looks something like this (after being programmed) -

upload_2019-8-12_9-23-33.png


Also keep in mind most processors these days will start up glitch free on outputs.


Regards, Dana.
 
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Thread Starter

vtc

Joined Apr 3, 2018
37
mBlock visual programming language and an Arduino Nano, Uno, even an 8
pin ATTINY85 would do, ~ 2% accurate timing.

Here is what i think are your basic requirements done in mBlock.

You drag / drop blocks, config, and the tool generates and uploads the Arduino "C" code.

View attachment 183684

The code it generates for you looks like this -

View attachment 183685

All you need is board, maybe an R in series with light sensor to make a voltage
divider to feed to the UP A/D pin and of course power.

If you use boards that have onboard xtal timing accuracy will be << 1%,
if ATTINY85 ~ 2%


Regards, Dana.
thank you for your appreciated effort ,i test a code on arduino nano it works well.
also i will test a code using attiny13 later.

Even better! no idle current wasted.
View attachment 183724
Since you mentioned your sensor is an open collector type:
The circuit on the left will do, but wasting a bit of power every time the object moves; could use a darlington style and reduces bias current consumptions.
The circuit on the right uses a P-Mosfet which consumes practically no current if you make that pull up resistor 10M.
Everytime the sensor senses a movement, it draws current (open collector), thus turn on the bjt / P-Mos which keeps the capacitor fully charged mean while the N_Mos conducts and turn on the lamp. The N-Mos remains on, uninterrupted till the capacitor is discharged via the 10M resistor (or 1M).
RL value depends on the supply voltage and bjt/p-mos max current draw capacity so that it wont burned up
i test the circuit with 470u, i got about 9.5 Min. thank you :)

If you don't want to program, use the CD4060 circuit.
It can be reset to restart the timing cycle.

j.png

hi @crutschow

the above circuit from the link you post.

As i understand the output at the selected range will be zero for the selected period after reset the counter then it will become high till the counter reset again.

so the ac lamp should be on when the output state zero.
and to turn lamp on for the selected period .
i should reset the counter either using a button or using my sensor.
?!

Regards
 
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