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74HC164 + ULN2803 LED CHASER

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DannyDilla

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So a buddy of mine (Hi Bernard!) on another forum suggested I use a shift register for an idea I had.

A little background--I'm pretty fresh out of college and I work with high voltages all day; mainly analog power, PCB Design, soldering, Hi-Pot and UL Certification. Digital Electronics is something I have never been good at but would love to be. I would love to design this PCB for the engineers I work with for christmas or something like that and I need some help.

The GIF I've attached is what the square wave and top bar will be doing. Whether or not the first, second, third, so on LEDs stay on until the end or they light up one at a time is not important to me--either would be cool. Maybe a comet effect would be ideal... By the way, there is a spot where all LEDs are off once a cycle is complete... I would prefer if that wasn't the case. I would like it if it continued with no breaks.

Finally, the outer green ring. I will take the total number of rising edges that light the LEDs (which won't be the same as the number of LEDs) and multiply that by 4 so that there is synchronicity--that is to say that the square wave and top bar go through 4 cycles while the outer ring comets once.

Any tips would be awesome!
 

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DannyDilla

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I had some trouble setting my password with my DannyDilla account, so if you wish to reply, please do it on this one! :)
 

large_ghostman

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Maybe I dont understand, but why not use a 4017 cascaded decade counter with a 555 trigger? you can add more than one together, if you want them all lit at the end, then the last toggle simply connect all the leds.....

But I got a feeling what I am thinking, and what you are thinking isnt the same thing.
 

large_ghostman

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You tube 4017 night rider or something like that, also called a decade counter. Have a look and see if you could use something like that.
 

DannyDilla

New Member
Ghostman....yeah the decade 4017 and 555 definitely seemed much easier, but it was the current sourcing that had me worried if I were to use the decade counters. Plus with cd4017's it would require a lot to do the square wave, bar, and eventually outer circle
 

audioguru

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The datasheet for the CD4017 shows how to cascade them so you can use two of them to make your 18 steps. 74HC4017 ICs provide much more output current to make the LEDs much brighter, or to drive a few LEDs at the same time.
But the ICs light only one LED at a time. The first LED lights then it turns off when the second LED lights which turns off when the third LED lights, etc.
 

ChrisP58

Well-Known Member
Doing it with straight hardware, the 4017 is the easiest, but you'd need an array of OR gates or diodes to 'pile' the output LEDs.
But I wouldn't use a 555. Since you need an AND gate for the cascade, I'd use a 4093 Quad Schmitt NAND gate. 2 gates to make the AND gate, and one gate to make the oscillator.

But if I were doing the design, I would choose a microcontroller. Probably a PIC16F722A.
And I would choose low current, high efficiency LEDs, so that I can drive most of them directly from the uC.

What is your intended power source? Battery or a wall wart?
 

large_ghostman

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I was thinking of transistor to drive the drive the leds, then each out put from the 4017 could just link back to the transistor pile. I didnt mention a micro because, unless your used to them it can be daunting. If you have no experience with micros, but you want to try it, Arduino is likely the easiest way in. It would alo give you alot of options, but you will ned transistors or whatever to drive the drive the leds. You could do it from the pins, but in most situations where people want plug and forget, I wouldnt do it that way.

Ultimately depends how comfortable you are with electronics, and how much you would like the ability to change/control things. Chris with the 4017 you could drop the AND gates, just use transistors and each successive pin links back the previous transistor base. Final pin in the 4017 cascade just resets back to the first.

Not well explained, but lets see what direction the Op is comfortable with.

OP I think the main message is, what you want to do is more than doable, it is mainly a question of how much you know or want to know. Plenty of ideas above all should accomplish what you want.
 

DannyDilla

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Yeah I worded it poorly. I mean my 555 will provide my clock signal to a 74HC164, which feeds into a BJT array (ULN2803A) which feeds into individual LEDs. There will be 54 LED total. Since part of the square wave will have all 4 (+ 1 on the top bar) lit up at once, I need something that can provide power.

I will have the option of two power sources. One will be the ~400V we work with--using a CUI PBK to step it down to 5V/3W (or 12V/3W) etc. I haven't totally chosen a voltage to go with but that much is arbitrary as I'll be able to supply it.

This file was given to me by a friend (hey Bernard!) but he's confused me with his improper labeling of the pin-outs.

Since there will be a heck-ton of LEDs on the board anyway--I'm not worried about that, but the less IC's i can have, the better. Everything will be SMD, and I can live with 7 ICs (for this part of the design). My power supply is not important at this point; and unfortunately I can't share it with you as it belongs to my company.

thanks everybody!
 

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large_ghostman

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No sorry, I meant I hadnt described what I was suggesting very well.
 

DannyDilla

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I think I just need to know how to cascade shift registers, and how to reset at a certain point (if say I want to reset the cycle before the last pin on the shift register).
 

ChrisP58

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I think I just need to know how to cascade shift registers, and how to reset at a certain point (if say I want to reset the cycle before the last pin on the shift register).
There are different shift registers, and the details of cascading them vary somewhat between them, but basically you feed the output of one to the input of the next.

But referencing your schematic from post #9: See also the datasheet the found here: http://www.onsemi.com/pub/Collateral/MC74HC164B-D.PDF

R55 and C1 form a Power On Reset that ensures that all the shift registers are LOW at startup. The inputs of the first SR (U1 pins 1, 2) are tied HIGH so that on each clock pulse (not shown) the HIGH state at the input progresses through to the next register.

The output of the last register of U1 (pin 13) is connected to the input of U2. The output of U2 is linked to the input of U3 the same way.

The reset pulse is taken from the third register of u3, (pin 5) which is the 19th register in the string. Like all of the previous 18 steps, pin 5 goes HIGH. This goes through an inversion provided by the transistor in U6 and is feed back to the Power On Reset circuit, and we're back where we started. If you want a different count length, take the reset signal from a different output. But it still needs to be inverted.

Note:
1) The 74__164 is available in different product families. The 74HC164 can run at 6V as shown on your schematic. The 75HCT164 is designed for 5V and can NOT run on 6V. So be careful not to get the two mixed up. Or you could run the system at 5 Volts and use either part.
2) If the output of the transistor in U6 (pin 16) that is used for the reset function is not shared with anything else, then D1 is not needed and can be replaced with a wire.
 
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