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 Forum index » DIY Hardware and Software
simple led chaser problem
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radek tymecki



Joined: Mar 22, 2009
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PostPosted: Thu Apr 04, 2013 11:18 pm    Post subject: simple led chaser problem Reply with quote  Mark this post and the followings unread

hi there

i've built a simple led chaser circuit and i dont know why it stops after 10-15 sec... dunno why? anyone can help me?

Posted Image, might have been reduced in size. Click Image to view fullscreen.

i've used hef4017 and ipaz7555

more info here
http://www.qrp.pops.net/leds.asp
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comrade_zero



Joined: Mar 05, 2009
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PostPosted: Thu Apr 04, 2013 11:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Try adding a 100k pull down resistor (to ground) on pin 14 (clk in) on your cd4017. Check the original Baby 10 sequencer article for more help if this doesn't help.
Good luck, hope this helps
c_z
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radek tymecki



Joined: Mar 22, 2009
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PostPosted: Fri Apr 05, 2013 1:01 am    Post subject: Reply with quote  Mark this post and the followings unread

i've connected 100k resistor to pin 14 and G... still stops
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comrade_zero



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PostPosted: Fri Apr 05, 2013 3:54 am    Post subject: Reply with quote  Mark this post and the followings unread

It looks like your reset pin is grounded. you have to clock it (high) to reset the counter.
If you google baby10 the schematic will help you out.
cheers,
c_z
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elmegil



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PostPosted: Fri Apr 05, 2013 4:52 am    Post subject: Reply with quote  Mark this post and the followings unread

Here's another discussion of troubleshooting this basic circuit (555 driving 4017):

http://electro-music.com/forum/topic-52774.html&postorder=asc

I would double check that pin 13 really is grounded, but that's because that was my mistake Very Happy
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PHOBoS



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PostPosted: Fri Apr 05, 2013 5:55 am    Post subject: Reply with quote  Mark this post and the followings unread

The only thing I see 'wrong' with that schematic is that the reset pin of the 555 (pin4) is floating, connect this to V+.
Not sure if that is what's causing it, you could test if the 555 is still running when the chaser stops.

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radek tymecki



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PostPosted: Fri Apr 05, 2013 6:57 am    Post subject: Reply with quote  Mark this post and the followings unread

pin 13 is grounded. ok i'll connect pin 4 to V+ and see what will happen.
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PHOBoS



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PostPosted: Fri Apr 05, 2013 8:14 am    Post subject: Reply with quote  Mark this post and the followings unread

comrade_zero wrote:
It looks like your reset pin is grounded. you have to clock it (high) to reset the counter.

Only if you want less then 10 steps, else you can connect it to GND and it will just loop back after 10 steps.

You can make it run just 1 time. Say you want 8 steps then you connect the 9th output to pin 13 (just as you would normally do with the reset pin)
Add a reset button and it will run 1 time everytime you push it, and hold on step 9.

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Last edited by PHOBoS on Fri Apr 05, 2013 10:44 am; edited 1 time in total
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bubzy



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PostPosted: Fri Apr 05, 2013 10:12 am    Post subject: Reply with quote  Mark this post and the followings unread

you could put an led on the clock, to see if the clock is still running, i would also check both chips.
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feggster



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PostPosted: Sat Apr 06, 2013 7:16 am    Post subject: Reply with quote  Mark this post and the followings unread

could it be from using a 7555 (cmos) chip instead of standard 555 ?
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PHOBoS



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PostPosted: Sat Apr 06, 2013 7:30 am    Post subject: Reply with quote  Mark this post and the followings unread

feggster wrote:
could it be from using a 7555 (cmos) chip instead of standard 555 ?

ah, I didn't notice that since I only looked at the schematic itself Rolling Eyes
but from a link on the page where the schematic comes from I got this
Quote:
If the RESET terminal of a 555 or 556 timer is not going to be used, it is normal practice to connect this input to the supply voltage. If the RESET terminal is left unconnected the operation of the timer will not be affected, however, the RESET of CMOS version of these timers should not be left unconnected as the inputs of these devices are more sensitive and this may cause problems.

so as I mentioned before, connect pin 4 to V+ that might solve it.

does one of the chips get warm/hot btw ?

Last edited by PHOBoS on Sat Apr 06, 2013 7:40 am; edited 1 time in total
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JovianPyx



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PostPosted: Sat Apr 06, 2013 7:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Using a 7555 is not the problem, it should easily work in this circuit.

Also, there is no need for a pull up resistor on clock input. Pin 3 of the 7555 is a totem pole so it drives to ground when low and drives to V+ when high.

The big no-no here (as has been pointed out) is that pin 4 of the 7555 is floating and should be connected to V+.

The note PHOBoS quoted about the reset pin refers to a 555 or 556 - which is a BIPOLAR part not CMOS. CMOS inputs (7555 is a CMOS part) should NEVER be allowed to float.

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radek tymecki



Joined: Mar 22, 2009
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PostPosted: Sat Apr 06, 2013 1:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

ok i'll remove 100k res and connect pin4 to V+. then we'll se what will happen
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radek tymecki



Joined: Mar 22, 2009
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PostPosted: Sun Apr 07, 2013 3:25 am    Post subject: Reply with quote  Mark this post and the followings unread

pin4 connected to V+ and circuit still stops
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stewpye



Joined: Apr 30, 2009
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PostPosted: Sun Apr 07, 2013 7:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Do you have an led via a resistor on the 555 output so you can see if that is still running? (or check it with an oscilloscope).

Stew.
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radek tymecki



Joined: Mar 22, 2009
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PostPosted: Mon Apr 08, 2013 2:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

i've connected led to pin 3 when circuit stopped. the led was flashing all the time... broken 4017?
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elmegil



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PostPosted: Mon Apr 08, 2013 7:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

have you tried a fresh battery?

Just grasping at straws, but....
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radek tymecki



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PostPosted: Tue Apr 09, 2013 9:35 am    Post subject: Reply with quote  Mark this post and the followings unread

i've exchanged 4017 onto new one and it works fine Smile thanks for help Very Happy
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