alternating flasher with variable on times for each led

[savarin]

Hello,
I would really appreciate a simple circuit to allow me to use a red and a green led where I can vary the on time of each colour.
That is, red on for 8 seconds whilst green is off then green on for 12 seconds whilst the red is off. This to continue until I turn it off.
Its to use as an exercise timer for an exercise bike so I can sprint like mad for 8 secs then coast for 12 seconds.(the optimum regime to loose weight and get fit)
My electronics knowledge is fairly low but I can solder up a simple circuit.
Many thanks
Charles

 

[ljcox]

I suggest that you use a 555 timer configured for an 8/12 sec duty cycle. Connect the red LED in series with a resistor between Vcc and the 555 output.

Connect the green LED in series with a resistor between Gnd and the 555 output.

There are plenty of circuits for 555 astables in this forum. Do a search for "555".

There are also internet sites that have 555 info. Some links have been posted in this forum in the past.

 

[savarin]

I suggest that you use a 555 timer configured for an 8/12 sec duty cycle. Connect the red LED in series with a resistor between Vcc and the 555 output.

Connect the green LED in series with a resistor between Gnd and the 555 output.

There are plenty of circuits for 555 astables in this forum. Do a search for "555".

There are also internet sites that have 555 info. Some links have been posted in this forum in the past.

Thanks, I thought it would be fairly simple but did not know what to look for.
What does Vcc mean?
And how do I recognise what circuit would be suitable?
As I said, my knowledge is very low
Charles

 

[on1aag]

Hi Savarin,

Here's a cheap and simple circuit.
Use low current leds.

https://www.alldatasheet.com/datasheet-pdf/pdf/26839/TI/CD40106.html

on1aag.

 

[savarin]

Hi Savarin,

Here's a cheap and simple circuit.
Use low current leds.

Thanks but unfortunately my knowledge is too limited to understand what you mean.

I've searched for astable flipflops, timers, on the web and found heaps but have insufficient knowledge to choose what one to use.

I will try astable 555 on here now.
Charles

 

[Gordz]

Take a look here, this may be helpful for you.

 

[ericgibbs]

Take a look here, this may be helpful for you.

hi Gordz,
I am looking and looking and looking, but I dont see anything helpful!

 

[on1aag]

Hi Eric,

hi Gordz,
I am looking and looking and looking, but I dont see anything helpful!

I think I understand what he means.

on1aag.

 

[ericgibbs]

hi on1aag,

Oh!!, I see it clearly now!.thanks ...

hi Charles,
Look at this circuit.
EDIT:
The 10Hz should of course read 10 Seconds.!

 

[savarin]

hi on1aag,

Oh!!, I see it clearly now!.thanks ...

hi Charles,
Look at this circuit.

Thanks, I've found a tute for the math (not that I get it yet) so a bit of swotting needed there.
I need a 40% - 60% cycle for 8 secs / 12 secs, correct??
to get this I play with the 2 resisters and the cap????
If I can work out the math I should get the values that way????
regards
Charles
who maybe getting in over his head.
and definitely will be when he starts looking at stepper motor drivers for his telescopes

 

[ericgibbs]

Thanks, I've found a tute for the math (not that I get it yet) so a bit of swotting needed there.
I need a 40% - 60% cycle for 8 secs / 12 secs, correct??
to get this I play with the 2 resisters and the cap????
If I can work out the math I should get the values that way????
regards
Charles
who maybe getting in over his head.
and definitely will be when he starts looking at stepper motor drivers for his telescopes

Hi Charles,
I misread that as 2 sec 'mad pedalling' and 8 sec 'cruising'.
I see now that its 8 sec and 12 sec cruising!, the logic still applies.
You require a 20 Sec total pulse period.

This 9 inch green monitor on my PC is hard to read in daylight.

EDITED:
Charles,
To give you an idea of the res/cap values required, a single 1M0 resistor and 20uF cap [ 2*10uF in parallel]
gives a total period of about 20 Secs, with a approx 50% duty cycle.

 

[savarin]

Time to play, what pin is power in? and will 9V be ok?

and is that a dual 555 timer chip? I cant find the number in the jaycar catalogue
Thanks
Charles

 

[Roff]

If you want adjustable duty cycle, here is an alternative. The other circuits can probably be modified for adjustable duty cycle also.

 

[savarin]

If you want adjustable duty cycle, here is an alternative. The other circuits can probably be modified for adjustable duty cycle also.

Thanks guys, I will have a play next week (just two classes to finish) and will report back how I went.
regards
Charles

 

[ericgibbs]

Time to play, what pin is power in? and will 9V be ok?

and is that a dual 555 timer chip? I cant find the number in the jaycar catalogue
Thanks
Charles

hi,
The ic is a CMOS 4093 quad nand with schmitt inputs.
9V will be OK, choose the resistors for the LED's to give about 10mA.

Ron's looks an interesting circuit, using the CMOS 555 timer.

 

[Gordz]

hi Gordz,
I am looking and looking and looking, but I dont see anything helpful!

Couldn't think of an excuse so It may have been more helpful if the link was there !! Sorry for the late reply I've been really busy.

 

[matk95]

or you can use this circut and change the 100k resistrors to variable resistors
it works with prity much any transistor (iv never used one that dosent work)
https://wild-bohemian.com/electronics/flasher.html
**broken link removed**