Simple electronics help

[Retropin]

Kinda feel really dumb asking this...

Im making an LED chaser/ flasher/ sequencer. Im pretty simple with stuff and so am using a 555 timer for clock and a 4017 decade for LED drive outputs.
OK... it kinda worked before i changed it, but LEDs are dull as crap, so i put a BC547 transistor in place to drive the LED.
Im doing a 10 output so on 4017 i have outputs 1,2,3,4,5,6,7,9,10,11.
8,13,15 are tied to ground
14 is clock
16 vcc ( 9v in this case)


If i use an LED to test outputs they flash once then off completely... nothing on other side of transistor ( output to base, 9v to collector, LED on Emitter).

Surely there should be a reset to trigger the cascade over again? or is it automatic?.. also i seem to be in reverse bias as if i use output of 4017 as grounding for test LED it lights up OK.

This is simple schoolboy stuff and ive cocked it

[studley67]

I MADE SOMETHING SIMILAR AS A KID AND HAVE STILL GOT IT.sorry bout the caps.it was an electronic dice from EA i think.if you added a resistor you had a led chaser,from memory.i will dig it out.

[ajlaird]

Something like this?

[Retropin]

The clock works on the 555... im falling over on the 4017 side.... pin3 flashes at clock rate and gives a good flash... all others are a tiny dull pulse.
Ive looked up the data on 4017 and pin 8 is to ground....13 and 15 ( reset and Clock inhibit) are to pin 11 which is the last flash.....mmm.. theres a fault.. clock inhibit should be low

[studley67]

i had to etch my own board,but yes

[mildflame]

i had to etch my own board,but yes

If you are wondering where it is its in my top draw in my room. I took the battery out for somthing   

[Marty Machine]

The 555+4017 are a classic led chaser design from waaaaay back....

Your pinouts are correct, and outputs will only briefly pulse on/off then move to the next pin....

Since you are using all 10 outputs, there's no need to force a reset, as it will auto-loop and count 1-10 again & again....

If you wanted say 5 leds to chase and repeat, you would wire the 6th output pin back onto the reset pin, the chip will reset immediately after the 6th led flashed and resume at led #1 again.

The 4017 used to drive STANDARD (5mA) leds back in the day with no trouble at all, but these days all the high-bright leds needs 20-50mA and i don't think the 4017 can source that much current on it's outputs. (i don't have the exact specs on hand).

Instead of using 10x transistors, you could use a buffer IC, such as the (cmos) 4049 or 4050, although you'd need a couple to cater for 10 outputs, although once again you'd need to confirm their current drive.
I'd prefer to use a higher current drive from a ULN2803 (8 outs), at least then you could drive relays or hi-watt leds and/or globes with no troubles in future ;-)

Hope it helps.
MM.

[Marty Machine]

Yep, your initial post said pin 13 was to ground, now you've found it's connected to pin 11 is incorrect. ;-)

[Homepin]

why would you bother with any of that rubbish  a PIC will do anything you want with less parts, more flexibility and far lower board space, repeatability and cost.….

[Marty Machine]

Not everyone into the basics of electronics know (or aware) of Pics.
Besides a few leftover chips are always hanging around in most hobbyists workshops.

This forum should be about Encouraging those who try, instead of slamming them down in flames.


baby steps......

[Retropin]

I cant program a pic... simple,
I need to get this working by tomorrow so im not going to relearn Basic in a night and then wish id done simple ( not in my case though)...


Ive found what my fault is.. or at least its symptoms.. im resetting on pin 3 which is 0 output... so it counts 1 then resets... friggin hate this proto board.. looks like a dogs dinner

[Marty Machine]

tie reset to ground (0v) and it will cycle all 10 outputs.

I'm sure you've just lost yourself on the breadboard somewhere.

[Homepin]

I guess it comes down to asking for some help a little earlier in the piece.....I can't program in basic either - far too complicated

[Retropin]

I appreciate your help Marty... im going to restart this tomorrow as my board is a now confusing.


Yes ive lost myself on my board... couldnt find the bread board so went straight in on the vero board. I got lazy and downloaded a CCT which i found out was wrong. Ive been trying to correct it  and just making a confusing mess. Ive since copied the data sheet for 4017 and i should have done the CCt myself...

8...13...15 all tie to ground... 14 clock from 555..

Thanks mate..

[Marty Machine]

8...13...15 all tie to ground... 14 clock from 555..
Thanks mate..

Yep, thats it, the most common mistake with veroboard is forgetting to count the pins 'mirrored' on the underside.
It's quite common to put 5v on pin 1 instead of 16, and put 0v on pin 9 instead of 8 (or 8 instead of 7 with ttl chips) etc etc.....BE CAREFUL with your pins hehehehehe   ;-)

MM.