how add hysteresis in my code

[tanveerriaz]

how i add 5v hysteresis in this code

[Mike Walne]

The state of the output pin is used to modify the reference values.

Mike

[ezflyr]

Hi,

Mike's answer is spot-on, but it may not be clear what he means? Basically, to add 'hysteresis', you've got to adjust the shift point depending on the current state. As an example, lets suppose to want to change the output state at 170. When you are below that value, transition will occur at 170, but when you are above that value, transition should occur at a slightly lower value, say 165. In this way, you won't constantly toggle the output if the input hovers about a single, fixed transition point.

Did I make this more clear, or just muddy the waters?

John

[Ttelmah]

It is difficult to have traditional hysteresis, since you are testing two thresholds at once. However for a single threshold, something like:

[Mike Walne]

I don't know exactly what you're trying to do. (You've not explained)

It appears, when ADC reading is between thresholds, you want pin_a5 high, else low.

Basically:-

If pin_a5 is low, you make the gap between the thresholds narrower, i.e. raise the lower threshold and reduce the upper one.
If pin_a5 is high, you make the gap between the thresholds wider, i.e. reduce the lower threshold and raise the upper one.

The shift required in the thresholds depends on your noise levels, and lots of other details you're keeping from us.

John's explained the rationale, Ttelmah's shown you how, for the more usual single threshold case.

Mike

[necati]

while(1){

set_adc_channel(0);
delay_ms(1);
adc_u=read_adc();

if (adc_u>= 170 || adc_u<= 240){output_high(pin_a5);
else{output_low(pin_a5);}
}

[Mike Walne]

[tanveerriaz]

i make a man voltage protecution circuit on a relay 170v to 240 voltage.
when voltage low 170 and up to 240 off the load. i need tune code for avoid chattering of relay.
hare is my code

[Mike Walne]

1) Do you have real hardware?
2) You have to assess the change in trip levels needed to stop chattering.
3) Is your input AC or DC?
4) Maybe we need to see your schematic.
5) Ttelmah has shown a way to do it.
6) You need to extend his idea to 2 thresholds.
7) Necati's suggestion is interesting.
8) When you're in-band the thresholds need to be further apart than when you're out-of-band.
9) Better indenting makes code more readable, and easier to follow.

Mike

[dorinm]

[tanveerriaz]

I need a circuit to protect my house electrical equipment
from main power up and down.
I have a prototype board for check my circuit.
I use 230v ac > dc and a resistance divider network to down voltage for adc input.

[Mike Walne]

[dorinm]

[tanveerriaz]

Here is my uncompleted work. When its complete I show it here.
I add a 3310 lcd to show voltage.
http://picturepush.com/public/12835620
http://picturepush.com/public/12835639
http://picturepush.com/public/12837662
http://picturepush.com/public/12837667

[Mike Walne]

A few comments.

1) You're not showing values for components, so we can't make any judgement.
2) The LEDs are wrong way round as shown on schematic.
3) There's a risk of destroying the relay driver device.
4) I hope you understand the risks working on live mains.

Mike