k then thanks..ill give it a try..but what about the 2004...what can i use instead of that 1..is there an alternative that i may have???

 

Nope, you don't have anything to substitute for the ULN2004A/ULN2804A - unless you have some transistors and resistors handy.

2N2222/PN2222 or 2N3904 or 2N4401 or 2N4410 are all NPN transistors that would do it for you; 2N2222 would probably be best in this case.

Use 470 Ohm resistors from the shift register outputs to the bases of the transistors. Ground the transistor emitters. Use the collectors to sink current from the cathodes of the LEDs. If you will only have 5v Vcc available, you will only be able to use 1 LED per resistor; you won't be able to run multiple in series.

 

omg...guess what..

that store is great...they had exactly what i was looking for the had the leds, but i couldnt really find any RGB LEDS, wasnt sure what to look for..they had some bi color..red and green...but just decided on clear better...

thank you so much for that tip...

i guess ill try my hardest to get it running today and hopefully it does go smooth...

i have another question...if i were to go back and buy the bi color leds to make it seem cooler...how would i put them together..cuz i did see that they had 3 legs...and how would the schematics look like if i wanted them to stay on the whole time and really just change color...

just for fun and try it out..if not then i guess i can stick with what youve showed me so far...

 

Use proper ESD handling procedures when dealing with those CMOS parts. Very easy to destroy them with just a tiny "zap" from static electricity.

The bi-color LEDs are probably red and green. They may have a common cathode or a common anode. You would need a different circuit to drive one than the other. Better to just keep it simple and use your individual LEDs, otherwise you won't finish in time.

Glad you liked the store. It's been years, and I can't even remember what it looks like.

Did they have the ULN2004A or ULN2804A? Curious what they were charging for them.

 

yea i know...

its pretty big...have loads of stuff and small kits that i can use to practice..its nice..but a bit cramped with stuff..lol

well i didnt ask about the 2304..i just asked about the 2004 and well they did have that one..

they were charging $1 each..

 

A buck each isn't bad for a store you can actually go into and get someone to help you look for stuff.

Be careful about collecting too much stuff; it can get out of hand in a hurry. Ask me how I know this.

Getting things organized can be a big chore, particularly if you were disorganized in the first place. Throwing everything in a big box is not the way to do it; you will waste lots of time looking for stuff before you give up and buy more.

 

yea i know...ive been thru that as well...but im a pretty organized person...and only purchase things i really need...

ok i have a question...and i have mostly everything..but ive noticed that some of the capacitors arent the same..i dnt seem to have the same 1...like the 1uF, or da 1M resistor...would i be able to use a substitute instead of those..i have other resistor potentiometers..but not that 1...

 

OK, do you have an ICM7555 or TLC555 timer? If not, which one do you have?

R2, R2, and C3 were set up to give you a range of speeds for the runway to flash. If you decrease C3, you will have to increase R2 and R3. R2 is basically there to keep it from flashing way too fast. There is a limit to how much you can decrease C3.

You could increase C3 to 10uF, and drop R2 to 10k, R3 to 100k.

What cap values do you have? And what pot values do you have?

 

yea i do have the 555 timer..

umm i have for the potentiometer...a 102..103 and 104..so im guessing they are 100 10K and 100K right..
and think i do have a 10uF

 

104 is 100k. Use that one and the 10uF cap. Use a 10k resistor for R2. If you don't have a 10k resistor, use anything from about 2k to 33k.

 

ok...well never mind i found the 1uF...
if i change the resistors would i still have to change the capacitors or could the capacitors stay the same

 

omg..i know im kinda bugging you and keep forgetting things..but i cant seem to find the 220uF..

i honestly thought i had that 1..but i cant seem to find that 1..is there any smaller that i can use instead..i seem to have 10uF, 2.2uF, 100uF, 47uF, and 100uF

can i use the 100uF
cuz like u said...their only there to control the speed right???

 

For the 220uF cap, you could substitute a 100uF cap.

The 220uF cap is to keep the board voltage stable. It handles the large transients that the 555 timer causes. The 0.1uF cap next to the 220uF cap handles the high frequency transients. You will see that very frequently; a large cap and a small cap in parallel with each other. But you can probably get away with using the 100uF cap.

I thought you said you were organized?

 

ok...well never mind i found the 1uF...
if i change the resistors would i still have to change the capacitors or could the capacitors stay the same

Why don't you look at the datasheet for a 555 timer, and see what the formula for determining the cap and resistor values might be?

I've already told you that if you change the cap, you have to change the resistor values to keep the timing the same. If I have to keep repeating myself, I'll start thinking that you don't bother to read what I'm writing.

 

no of course i read everything and kinda understand you but the thing is that at first i was just changing the resistor and 1uF cap...but then i just ended up changing the resistors...but yea i get you..

im sorry its just that im trying so hard that its stressing me out and i forget some of the things that you are telling me..and dont bother to look back at the last posts..ill try to do that more often...

but uve already been super help...thanks so much..well i mostly have everything together..i just need the function generator and some extra resistors...ok so now that im ready you said to determine what resistors i might need after the LEDS depend on:

(v supply - (Vf LED total + da 0.7 drop from the 2004)/ desired current...

so if i use 12V or i would say 15 V top...and i am using white LED which were about 3.4/20mA
i would end up needing the resistors to be about 225...so would i be able to use a 220 ohm resistor..i have some of those...

 

Why do you think that you need a function generator? The 555 timer is providing the clock for the circuit. It just needs a supply voltage.

OK, if your LEDs have a Vf of 3.4v @ 20mA, then their total Vf would be 6.8v, add in the 2004 drivers' 0.7v drop for 7.5v total.

If you used 220 Ohm resistors for current limiters, what voltage would you get across them if you passed a 20mA current through them?

Think Ohm's Law.
Once you find that result, then add it to the 7.5v that the LEDs + the ULN2004A driver drop. Then you will know your appropriate supply voltage.

You will also be able to figure out what will happen to the current through the LEDs if you use a higher Vcc.

You need to know how to figure this stuff out for yourself. You should already know Ohm's Law backwards and forwards. If you don't, you need to start learning it right away.

 

well i need the function generator to add the 12V to the circuit..

apart from that i only have the adapter for the 9v battery...

yea your right...i do know ohms law...

thanks

 

ok...i think i have almost everything ready...

i already connected everything...and i used a 9V adapter and applied it to my breadboard but nothing really happened...

acording to what you showed me...ok im applying 9v of supply of course...

9v minus the 3.4+3.4+.7 from the leds divided by da 20mA of current...then all of that would leave 9v-7.5/.002
it equals 75 ohms that is required
so since there are no 75 i used 5 82 ohm resistors....but it does not seem to light up at all...is there anythin that i might be missing...
i already added the V+ to pin 16 and grounded pin 8 on the 4015...and checked all the wiring.ill send u a pic of how it looks...

 

What voltage are you getting on the battery when it's connected?

Make certain that you don't have pins 15 and 14 shorted on the 4015. 15 is D in; it should have 9v on it. 14 is RESET, it should have 0v on it, except for a brief moment when all the LEDs are lit and one more clock outputs from the 555.

 

Keep in mind that 9v "transistor" batteries are rather poor power sources for this kind of thing. They have a very high internal resistance (several Ohms); they were designed for very low loads. A typical alkaline 9v cell might be rated for 500mA, but that's over a 20-hour discharge rate. 500mA/20 Hours = 25mA constant load. However, you're trying to run six strings that will total up to around 120mA when they are all on. It should work for a test, but you wouldn't want to leave it running very long like that.