Highwrath

I am not only a noob but completely ignorant regarding this kind of electronics (all kinds really). I am trying to create "critter lights" for my back yard as an evening feature. I put some boulders together in the form of a "cave" with the idea that in the evening when my landscape lights come on I could have some "critter lights" create a little interest. The opening to the cave is about 8"x10." A friend of mine suggested a ciruit board for the lights and timing mechanism. The low voltage transformer provides 12V and I have 58watts remaining after the landscape lights. I can not describe in words what it is I am looking for so I created a gif image.

If anyone can help with a schematic for this sort of thing or other resources that might help I would greatly appreciate it.

HarveyH42

Threw this together kind of quick, mostly just a basic idea. You will need to play with the values some to get the effect you want.

A 555 is used for a clock source to feed a binary counter. You can have up to 12 pairs of 'eyes' if you wish, just remove/move the Reset line. I used kind of a high value for the current limitting resistors, but you might want to go even larger, as I don't think you want the LEDs to be full bright, othe wise they will light up the cave interior.

Attached Images

Critter.jpg (84.2 KB, 38 views)

Hero999

I would also recommend the 4060 which includes the oscillator so there's no need for a 555.

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mneary

Since the 4040 and 4060 are ripple counters, each set of eyes will flash at half the speed of the one before it: the first flashing once per second, and the last flashing once every 2 hours or so.

With a 4017 and a couple of XOR gates you can make a linear feedback shift register. I just searched the web and didn't find any simple circuits, but I'm sure the other members here can come up with one.

If you have Power Point, this link would help.

Roff

I don't think you can make a LFSR with a 4017. The 4017 is a 5-stage Johnson counter with decoded outputs. A LFSR requires a shift register and one or more XORs.

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Ron

Roff

Here's an 8 bit LFSR that should work. I simulated it, but I have not built it. Eight bits is probably overkill, but it might be fun to play with.

Attached Images

LFSR 8 bit.PNG (32.2 KB, 19 views)

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Ron

mneary

8 bits means 8 pairs of eyes

Sorry about the 4017 suggestion. Should have looked it up.

TON80

Will the 4040 take 12V?

HarveyH42

It should, most 4xxx series go to 15 volts...

http://www.datasheetcatalog.com/data...CD4040BC.shtml

Oh, didn't mention but my software does show chip power connections (maybe it does, just never found/looked for the option).

TON80

I'm using an RCA CD74HC4040E. Data sheet says Vcc -0.5v - 7.0v. Looks like I need to get a "B".

OutToLunch

too much complication for blinky eyes. I've used Bill Bowden's fading eye circuit to make eyes in the bushes for halloween - good effect. The circuit configured as shown will fade the LEDs on and off. You can also connect it so that they blink on and off.

http://ourworld.compuserve.com/homep...5.htm#eyes.gif

Roff

No, you need a CD4040 (Motorola's part number is MC14040B).

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Ron

Roff

You neglected to mention that you need one circuit per pair of eyes. To make the eyes flash, connect the base of the transistor to the output of the other op amp (pin 7 in the schematic). You might change the value of the LED current-limiting resistor to meet the needs of your LED, especially if you use a different supply voltage.

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Ron

HarveyH42

Actually if you wire the fading-eyes circuit up to cross-fade, you can get two seperate sets of eyes per circuit. Using a quad opamp LM339(?) would give 4 from a single chip. It's a nice circuit, I changed it around some and used it for my first RGB LED project, and still think it gives the best mix of colors, wide range of hues. The ATTiny13 version I use now is good, and it's really part simple, 8 pin MCU and RGB Led, 3.6 v battery.

I'd don't remember my 74xx stuff, been too long, and too many variations. Let's see, there is the straight 74xx, S, LS, AC, ACT, HC, HCT... Feeling like I missed a few.