Toothbrush timer help

[Uma!r]

Hi
I will very grateful if you can help. I am making a toothbrush timer for my electronics project. I have done a Monostable circuit using a variable resistor, capacitor, push to make switch and 4 Nand Gates. I have used an IC instead of the 4 Nand gates in my real circuit but I can’t remember what the IC is called. It goes like input, input, output, output, input, input, voltage etc.
The buzzer goes off after 3 minutes, which tells the user to stop brushing. But I want to add a counter circuit to the toothbrush timer so the LEDS light up one after the other with a delay of 30 secconds, so the user can see when the time is about to run out. i plan to add 6 LEDs which will add upto 3 minutes. Can anyone tell me where I have to connect the counter? is it posiable the timing of Leds change at the sametime as the buzzer if the variable resiton is adjusted. And do you have any ideas that I could add to the Toothbrush timer? I can add a diagram if you need one?
Thanks you

 

[Russlk]

A circuit diagram would be helpful. You may find some useful info at this site: **broken link removed**. Also, try to get hold of a TTL data book.

 

[Noggin]

stick with the buzzer or you'll go cross eyed

 

[Uma!r]

PIcture

Hi
Here is the diagram of my timer circuit, i need to add more stuff. any ideas?
Thanks

 

[Nigel Goodwin]

For a start I would add a couple of resistors, one in series with the pot (and where will you find a 60M pot?), because if the pot is turned to minimum resistance pressing the button will short the supply out. Also I would add a current limiting resistor in series with the switch, shorting the 47uF out with the switch will burn it's contacts quite quickly.

 

[bogdanfirst]

the NAND gates are probably CD4093 Schmitt trigger nand gates. :shock:

 

[grrr_arrghh]

hi.

you could use the nand gates in a 4011 IC or the NOR gates in a 4001 IC (the two input pins are connected together so it has the same affect)

i have, however, created an alternative to your circuit, useing a 555 timer IC and a 4017 IC. The 555 feeds a pulse into 4017 every 30 seconds(ish), which advances by one count to light the next LED. when the sixth LED is lit, the buzzer sounds, and the counter is frozen on that output, until you turn off the counter.

**broken link removed**

this may be of no use to you at all, but it may give you some ideas.

hope it helps

Tim

 

[Uma!r]

Thanks grrr_arrghh
That circuit looks great; I am going try and a variable resistor so the user can change the timing of the buzzer. I might even add an extra counter to control extra LEDs, just for visual effects, like 6 LEDs flashing.
Thank you very much
I will post my circuit design after I have made the modification; I really appreciate you taking your time to draw the circuit diagram. Thanks again

 

[Uma!r]

hi
i have tryed making the circuit, but it keeps on blowing up for some reason? can anyone help me ?
thanks

 

[Nigel Goodwin]

What keeps blowing up?.

 

[Uma!r]

hi
the decade counter and thr top LED keeps blowing up.
thanks

 

[grrr_arrghh]

i assume you are mocking up the circuit in Crocodile Technology, like the first one.

two things.

one, go into space (or options) and then logic. Enuse that the selected option is '4000 Series Logic'. Also change the 'supply voltage' to 9v (or whatever you are using).

two, ensure you are using a 4017 IC, not a decade counter, and the enable pin is inverted. (if you can only get a decade counter, reply, and i'l show you what you need to change)

glad to help

Tim

p.s. did the circuit appear ok, as in my broser it has been replaced with a small box with a red cross in it...!?!

 

[Uma!r]

First circuit completed!

Hi Tim
Thank you , I inverted the enable pin and it started to work.
With out your circuit I wouldn’t have been able to do this circuit bellow.

The circuit is all complete accept that I need to add a power light LED with a push to make switch. I am still trying to calculate what Resistor to use!

Feel free to make any suggestions on how to improve my circuit. any idea on the display part?
Thank you

 

[grrr_arrghh]

hi

always glad to be of help

i assume u meant to post a picture of your circuit...?!? lol, never mind.

ermm, for any single LED, put a 330R (R means ohms) resistor in series with the LED (although anything up wards of a 220R will do it, but going to high will dim your LED)

you say "a power light LED with a push to make switch", i'm not sure what you mean, but if you mean that the LED lights up when you press the switch, to tell you if you have any battery power left, then simply put the switch in series with the LED and resistor. Alternativly, miss out the switch, and just leave the LED lit all the time (it won't draw very much power, especially if you are using a 9v PP3 battery)

any other questions, let me know

i'd still b interested to see your final curcuit

Tim