first time useing a 555 timer

chiver · Post by **chiver** » Fri Nov 09, 2012 12:07 am

I picked up the Bag-o-chip from Modelers brand and it was a great buy. now i have you tubed how to build a blinking circut. I have it just as it was laied out on the drawings, and i've trried alot of different resistor combos.

it lights up when pin one is not connected.
http://i1170.photobucket.com/albums/r52 ... DB16F1.jpg

but not when attached:
http://i1170.photobucket.com/albums/r52 ... 57CE58.jpg

i've built it 3 times with a new chip every time and still the same. now yesterday i had to working in this config, but for some reason now it wont.

someone please help. once i get this working there is another video i founf or then make it strobe. but first i need to get this thing going.

thanks in advance,
chive on

Sloucher · Post by **Sloucher** » Fri Nov 09, 2012 8:05 am

The only thing I see that I'd change is to fit a small, 0.01uF (10nF), capacitor between pin 5 and ground. Pin 1 must be grounded or the internal comparators can't do their thing.

Does the led flash or is it on continuously when it lights? Is the electrolytic cap attached to pin 2 the right way round - it looks like it could be back to front.

Slouch

chiver · Post by **chiver** » Fri Nov 09, 2012 8:43 am

tyhe video i watched said to leave pin 5 be, that it dosent do anyhting for a flsher circut, when i remove the ground from pin one the light comes on and is a stedy on, when i replace it, it turns off. i did have it blinking the other day with all the same values and parts. as i said i tried to rebuild the circut with new parts to the same effect. i have not tried to reverse the electrolytic cap just yet. but im pretty sure its on the right way.

Sloucher · Post by **Sloucher** » Fri Nov 09, 2012 9:16 am

Pin 5 should really be tied to ground when using the 555 as a timer as pin 5 is the reference voltage input. If its left floating it can cause the timing to drift all over the place.

Seems odd it worked before and not now though

. What fllashing rate are you aiming for Chiver? Let me know what time on/off you're after and I'll come up with the resistor/capacitor values and breadboard test it for you.

Have a look here:
http://www.555-timer-circuits.com/
It may help you to understand the ic and its applications a bit.

Slouch

PS Apologies in advance if the reply duplicates itself. My (not very) smart phone doesn't seem to have sent my original reply

chiver · Post by **chiver** » Fri Nov 09, 2012 9:51 am

I'm trying to get a strobe for a defiant class ship, it would be off for about 2 seconds and have a very quick flash.

Sloucher · Post by **Sloucher** » Fri Nov 09, 2012 10:08 am

For that sort of flash rate you'll need:
C1 elect cap = 100uF,
R1 (the resistor from +v to pin7) = 2.7 Kohms,
R2 (the resistor from pin 6 to pin 7) = 27 Kohms
and
you will also need a diode (1N4008 should do it) in parallel with R2 with the band on the diode nearest to pin 6. The diode is needed because you need a duty cycle of less than 50% (ie the led is off longer than it is on).

The values above should give you around 1.9 seconds on followed by a 0.1 second flash.

HTH

Slouch

chiver · Post by **chiver** » Fri Nov 09, 2012 10:14 am

A lot, I'll give it a try at lunch, I don't know if I have a 27 ohms but I'll use as close as I can

Sloucher · Post by **Sloucher** » Fri Nov 09, 2012 10:33 am

Its 2.7 and 27 Kilohms Chiver - thats a factor of 1000

and don't forget that diode

I'll try a few bits and pieces as well l8r

Slouch

chiver · Post by **chiver** » Fri Nov 09, 2012 12:07 pm

I am trying it now, but not it is lit when pin 1 is on ground( yesterday it wouldn't) I havent connected pin5 yet and I did switch the cap around, still no blink

chiver · Post by **chiver** » Fri Nov 09, 2012 12:11 pm

Pin 5 connected no blink

chiver · Post by **chiver** » Fri Nov 09, 2012 12:18 pm

I do not have a 27k ohm but I do have a 10k ohm, so I will give that a try

chiver · Post by **chiver** » Fri Nov 09, 2012 12:21 pm

Does the diode need a resistor?

chiver · Post by **chiver** » Fri Nov 09, 2012 12:26 pm

No dice, no flash or blink, just lit stedy picture to come

chiver · Post by **chiver** » Fri Nov 09, 2012 12:32 pm

http://i1170.photobucket.com/albums/r52 ... BECCCB.jpg

I did get a blink, but it's more of a flicker every 19 seconds

chiver · Post by **chiver** » Fri Nov 09, 2012 12:36 pm

I only have a 4.7uf cap

Sloucher · Post by **Sloucher** » Fri Nov 09, 2012 12:54 pm

Sorry for the delay, travelling home!

Let me throw a breadboard circuit together and see if I get any problems. Be back in a coupla hours (gotta go and fetch the wife from work now!!)

Sloucher · Post by **Sloucher** » Fri Nov 09, 2012 2:43 pm

OK Chiver - just breadboarded this:

http://www.flickr.com/photos/38926882@N ... hotostream

Its not quite the speed of flash you want (and I know the led is blue - it was just lying around!), but its just to prove the circuit to you.
Cap is 100uF
R1 is 2K
R2 is 20K

If you only have a 4.7uF cap, try using R1 = 20K and R2 = 560K

If you change just one value it'll have quite an effect on the flash rate (see the link to that 555 reference site I posted earlier). Have another go, it will work - honest!

Slouch

PS if anyone needs a StarFleet flasher circuit, anti collision beacons and strobes, I make one using a 556:

http://wiredfx.co.uk/nav_lights

Its got a proper pcb now as well

chiver · Post by **chiver** » Mon Nov 12, 2012 3:20 pm

WE HAVE A BLINK, but no strobe:

here's a vid;

i apologize got the shakiness of it, i tend to get a bit nervous on camera

chiver · Post by **chiver** » Mon Nov 12, 2012 3:22 pm

Video: http://i1170.photobucket.com/albums/r52 ... E2E622.mp4

Sloucher · Post by **Sloucher** » Mon Nov 12, 2012 7:22 pm

Hi Chiver

Nice video - and yes the name's ok!!

Two things to mention - first don't connect pin 5 to ground directly. That'll just set the control voltage to 0v and so the circuit won't flash at all.

Secondly, can you check your resistor values and double check its all wired as per the 555 astable wiring diagram? Check the 555 data sheet for the correct config and then just add the diode in parallel with R2. The values you mention in your video actually give a calculated flash rate of 1.3 secs on and only 0.06 secs off which isn't what I'm seeing there.

You are actually using 400K for R1 and 20K for R2. You could try swapping them around, ie 400K for R2 and 20K for R1. That will give you, in combination with the 4.7uF cap, a flash rate of 1.3 secs off and 0.06 secs on.

Other than that, I'm afraid you'll have to source some new resistors and capacitor of the values we talked about before!

Swap those resistors, add the small cap (or leave it out if you like) and and see what you get.

Best of luck
Sloucher

chiver · Post by **chiver** » Mon Nov 12, 2012 9:51 pm

At the risk of looking stupid, are these one in the same thing? Just different values of course;

http://i1170.photobucket.com/albums/r52 ... 342A1B.jpg

chiver · Post by **chiver** » Mon Nov 12, 2012 10:09 pm

o0k well i tried two things.

1) i swaped out the blue cap for the brown one(153 value)

2) switched r1 and r 2 with the dioed in parrell w/ r2

now i have no blink

even aftwer replacing the blue one, and pin 5 has be disconnected since i didnt have a blink with it any way

Sloucher · Post by **Sloucher** » Tue Nov 13, 2012 5:00 am

Hi Chiver

OK, lets deal with the capacitors first:

The larger blue capacitor is what is called an electrolytic, or polarised capacitor. It can only be charged in one direction. In other words, for our purposes, it works one way round but not the other. In the case of the 4.7uF capactor you have, the positive lead is the longest of its two leads and the negative lead will have minus signs on the side of the case adjacent to the lead. The negative lead goes to ground, or 0 volts, the positive lead goes to pin 6 of the 555.

The smaller, orange, capacitor you have there is a ceramic (non-polarised) capacitor of 15nF, or 0.015uF. That capacitor can be used to go from pin 5 to ground, or 0 volts, and can be either way round.

Next, lets make sure we're all familiar with the 555 astable (flashing) mode connections and which component is which:

http://www.flickr.com/photos/38926882@N ... hotostream

Using that diagram, with the components you have (what other value resistors/capacitors do you have around?), making sure you add a diode in parallel across the whole of R2 (with the black band nearest pin 6).

Use 400K for R1 (two 200K in series) and 20K for R2 (two 10K in series - again don't forget the diode will have to go from one end of the two resistor chain to the other). Use your 4.7uF electrolytic capacitor for C (remember the polarity) and your small orange capacitor for the 0.01UF cap on the diagram.

Give it another go, and in the meantime I'll sketch up a breadboard diagram for you if you think that might help?

Cheers
Sloucher

Sloucher · Post by **Sloucher** » Tue Nov 13, 2012 8:03 am

Chiver,

try this:

http://www.flickr.com/photos/38926882@N ... hotostream

Sloucher

BTW, so as not to hog the board, might be best to continue this thread by PM, unless the mods et al have no objections to carrying it on here if its of help to others as well?

Sloucher

starsend · Post by **starsend** » Tue Nov 20, 2012 5:15 pm

You're obviously in good hands here with Sloucher, but I just want to insist that you need a small capacitor between pin 5 and ground. Otherwise you will see massive fluctuations in frequency and kind of "blinking". And if you have more than one circuit in your ship, all of them will start acting up unless you ground pin5.

chiver · Post by **chiver** » Tue Nov 20, 2012 7:09 pm

He did mention that, and we got it working, I will be posting a video on my defiant class wip thread