Help With Blinking LED

ENT2151 · Post by **ENT2151** » Thu Nov 09, 2006 3:48 pm

Hello,
I am building a life sized model of a DC-15 rifle from Star wars. The plan is to have a Ultra Bright blue LED at the tip so it will illuminate like in the movies, it will be attached to a momentary push button switch. The only poblem is that it needs to blink in, i think its 0.7 second intervals, thats why a self blinking LED wont work. Any suggestons on how i should make the LED flash would be helpful, thanks.

Sparky · Post by **Sparky** » Thu Nov 09, 2006 4:53 pm

It depends on how you want it to blink. A flash or a pulse on and off. Both circuits can be made so that you can adjust it for the proper rate. Take a look in the Electronic Circuits Help sticky thread.

ENT2151 · Post by **ENT2151** » Thu Nov 09, 2006 5:01 pm

It would probably work better with a pulse rather than a flash. i looked in the "electronics circuit help" post and i was unable to find anything helpful, though i might have missed it. what would i use to make a pulse circuit?

Sparky · Post by **Sparky** » Thu Nov 09, 2006 5:56 pm

There's a good reference for a 'gentle pulsing' circuit from some computer moders in the UK, let me find the link. . .
http://www.cpemma.co.uk/throbber.html

The one thing that is hard to find is the bipolar cap, it from digikey, and there's only one supplier, panasonic. Also the '4K7' ohm reistor, I belive is a 4.7 Kohm, or was ti 4.7, now <I>I</I> can't remember.

The trick was to find out that they call it a bipolar cap. other wise you'll neve find it as a non-polarized cap.

The smaller uF ratings are easy to find since they are used in crossover filters for car stero systems.

We used 5 of these in model project and they work great.

ENT2151 · Post by **ENT2151** » Thu Nov 09, 2006 6:12 pm

ok, that looks like it could work, the ony problem that i am having is that it talks about an 8 pinn DIL socket, one which i would guess that a chip like a 4060 would go into, except that is not shown on the circuit diagram.
also it uses 12 volts, do you know if there is a way it can be changed so it only uses 9 Volts?

Sparky · Post by **Sparky** » Thu Nov 09, 2006 6:24 pm

It should work off 9 volts I believe the timing is voltage indepentent, as long as you adjust the resistor on the output so your LED still gets the voltage and current it wants. I think I tested the breadboarded one at 3.3 volts once. I can double check it if the 3.3 votl regulator isn't toast.

The DIL should be DIP, a DIL is just 2 rows of pins right next to each other. What they wnat is just a DIP IC socket. You can make it without the socket if you're brave. My suggestion is to breadboard it first to get your layout, then make a board, and not use a socket. A socket takes up more space, but allows you to remove the chip if you think you burned it out, also it helps you not solder right to the chip:

Some solder irons give off transisent voltages and can damage a chip while you're sodlering it in place (get a good iron). Also you have to heat the pin to solder it, if you're not so good at soldering you could heat damage the part. This why sockets are used. Just get an 8 pin socket for a standard DIP IC.

Ah here's one:

http://www.jameco.com/webapp/wcs/stores ... tId=683104

ENT2151 · Post by **ENT2151** » Thu Nov 09, 2006 6:30 pm

Ok, that clarifys the 8 pin socket, and the voltage. Though i still dont know how that would fit into the diagram/schematic on the site. it doesnt show where the 8 pin socket would go. it shows it in the picture and the computer layout, just not the schematic.

macfrank · Post by **macfrank** » Thu Nov 09, 2006 7:00 pm

ENT2151 wrote:Ok, that clarifys the 8 pin socket, and the voltage. Though i still dont know how that would fit into the diagram/schematic on the site. it doesnt show where the 8 pin socket would go. it shows it in the picture and the computer layout, just not the schematic.

A schematic typically doesn't show you the socket; in most cases the socket is "invisible" - it's just there to make the IC removable. For example, look at the op-amp inputs at U1a. You can solder wired directly to pins 2 and 3 of the IC, in which case it becomes very difficult to remove it if it goes bad. Or you can put a socket in place of the op amp and solder to pins 2 and 3 of the socket. Now you can replace the IC without having to unsolder and resolder anything.

Frank

ENT2151 · Post by **ENT2151** » Thu Nov 09, 2006 7:04 pm

ok, i think i have found everything, except the C3 100nf ceramic capacitor. do you have a suggestion where i might find one, or if that is a typo?

macfrank · Post by **macfrank** » Thu Nov 09, 2006 7:36 pm

ENT2151 wrote:ok, i think i have found everything, except the C3 100nf ceramic capacitor. do you have a suggestion where i might find one, or if that is a typo?

100nf = 100 x 10^-9 = 0.1 x 10 ^-6 ; it's just a 0.1 uf capacitor.

ENT2151 · Post by **ENT2151** » Thu Nov 09, 2006 7:40 pm

ok, then the next question is how many volts would it be? the parts list only says 100nf ceramic. and nothing else is mentioned about it. also, do the potentiometers/variable resistors need to have a +/- 5% tolerance as well, or will it work if they have a +/- 20% tolerance?

macfrank · Post by **macfrank** » Thu Nov 09, 2006 8:22 pm

ENT2151 wrote:ok, then the next question is how many volts would it be? the parts list only says 100nf ceramic. and nothing else is mentioned about it. also, do the potentiometers/variable resistors need to have a +/- 5% tolerance as well, or will it work if they have a +/- 20% tolerance?

The circuit is powered by 12 volts. when designing or building a circuit, you want to get capacitors with double the rating of the highest voltage that they'll be exposd to. In this case, get capacitors rated at 25V.

For this circuit, I don't think resistor tolerances are critical. The pot tolerance is only for the full range; again, not critical.

Frank