i dont know if you are using seperate resistors instead of rv2 a variable,
if variable a limit ressister needed as these will present a short if turned to minimum,(rv1 as well)
im off sick (nothing serious) at the moment,so if im a pest tell me to clear off,catch you tommorow (im on gmt)
regards
dougal

 

yep, makes sense i just reverse the comp inputs?
i dont know if you are using seperate resistors instead of rv2 a variable,
if variable a limit ressister needed as these will present a short if turned to minimum,(rv1 as well)
im off sick (nothing serious) at the moment,so if im a pest tell me to clear off,catch you tommorow (im on gmt)
regards
dougal

 

oops, sorry

 

i wonder if bill means working back from the 555 and changing polarity of comparitors to suit, as (rough) pic
d

 

marx
redrawn as your circuit i think .
couldnt the outputs look something like this.attachment

busy for the next couple of days, wiil you keep us posted
dougal

 

Sweet think I'm going to build the circuit with two different LEDs and implement the 555 in a simpler fashion.

I could probably put this circuit together the way Bill has suggested but I doubt I'll have enough time before its due to have a clear picture in my head of what its doing.

 

It's all part of the fun. Let us know what you come up with.

 

Decided to put up what I've done so far, still missing some necessary components but hoping you can let me know if I'm heading in the right direction.

Obviously the 555 section isn't complete, but would the 555 be triggered and reset the way I have shown? So triggered when B is high and reset when B is low.

 

Have to admit not feeling to confident about that circuit. My head is Fried calling it a day.

 

hi marx
you dont need us,looks good, if you want i'll check it out on the simulator later on.

a useful tip, a 555 as an oscillator can be started and stopped by taking the reset pin- pin 4, high or low.
high to start,-low to stop.
dougal

 

the link between pin 2 555 to top led ?

 

sorry, missed your text i,ll have to get a bigger screen,

 

r5 -r6 = .1 collector current approx == led 20 ma + buzzer current, at voltage, say 18v ? .ohms law should give you values for these resistors.

also need a limit resistor on led circuits, ohms law again- 20-30 ma @18v supply? assuming 2v fv= 820 ohms. 1 watt , 1k should be ok = +buzzer current.

 

ps
LM339 looks like its limited to only a couple of millimps, so R5 AND R6 must be chosen accordingly,

 

"LM339 looks like its limited to only a couple of milliamps,"

sorry max sink 18ma

 

Don't see the scheme to flash the LED.

 

hi marx
you dont need us,looks good, if you want i'll check it out on the simulator later on.

a useful tip, a 555 as an oscillator can be started and stopped by taking the reset pin- pin 4, high or low.
high to start,-low to stop.
dougal

Mate if you put it through a simulator once its close to being finished that would be great!

Don't see the scheme to flash the LED.

You mean for resistors and caps around the 555? Haven't done that yet, just wanting to know how the circuit leading up to the 555 is looking.

 

Okay how does this look.

 

high marx will do, how precise do you need, i got 2.8 k
6.2 k
1.8 k
on divider
giving 3v dead and 13.3v so far ,
maths is not my strong point,

have you decided on supply voltage ,

339 is ok up to 20 odd volts , 555 up to 18, i think, so these will need checking
still dont understand the link on pin 2

wondering about a seperate tr for buzzer,

 

The Link on Pin 2 is to sound the buzzer when B goes high (below 10v)

Supply voltage will be 18v.... 2x 9 volt batteries. Not sure if I should regulate that down to 15V say?