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3V LED Chaser project

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Hi Andrew,
A transistor multivibrator usually works fine with a supply voltage of 6V or less. Above 6V the transistors would need diodes in series with the emitters to protect their b-e junctions from reverse overvoltage breakdown.
But the output high-going switching time of a transistor multivibrator may not be quick enough for use as a clock signal for a 74HCxx device that has a maximum recommended input risetime of only 400ns.

The reasons that I used a Schmitt trigger inverter as a clock oscillator for this project are:
1) Its output risetime is only about 19ns.
2) I can easily control its duty-cycle for PWM brightness adjustment.
3) A Cmos Schmitt trigger oscillator uses hardly any supply current.


Hi Guys,
I went to my local parts store to buy some more blue ultra-bright LEDs. They didn't have any because someone must have seen my post and bought them all! (How did Dazza get up here?) ;D
I ordered them, they will have lots tomorrow. I bought some green ultra-bright LEDs there. Their brightness at only 17mA is awesome like the blue ones. It is too bad that they need about 3V minimum to light. Therefore the project needs a 6v battery (dropping to 4V when drained) instead of a 3V battery for red LEDs.
[move]Ultra-bright LEDs are awesome! [/move]

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Hi Guys,
Today I finished another (I've lost count) chaser project. This one is also "6V" like the ultra-bright blue ones and uses green ultra-bright LEDs.
Wow, wow, wow and wow again! Is it ever BRIGHT!
I thought the blue ones were bright. This one is amazing, like little green magnesium explosions going off. I was right, our vision is most sensitive to green.

I changed the current-limiting resistor in the blue ones and this one down to 75 ohms, for a peak current of 24mA. The absolute maximum continuous current output rating for the 74HC4017 is 25mA, but my circuit pulses the outputs for only 30ms (or less when dimmed) so it is very safe.

Oh, oh. For a moment my whole room lit up. I have 5 chasers running and they must have synchronized for that moment.

I haven't seen the green one in the dark yet, 'cause it's dusk right now. I can see it reflecting off my monitor screen (it's about 6m behind me) and I bet it is bright enough to light-up the house far across the street! ;D

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Hi Guys,
Oh, oh. I found a problem with the "6V" version of my ultra-bright LED chaser circuit:
It eats batteries!
My ultra-bright blue one wasn't as bright anymore because its battery voltage dropped to 5V (it started at 6.2V). I've had it for a month and turn-down its brightness and speed overnight so I thought it would last for months. I forgot to measure its current when turned-down like I measured the 3V ones that I posted as a project.
It draws nearly as much current when turned-down as it draws at full brightness and speed!

My circuit pulses the LEDs for only 30ms with a long pause between, so the average LED current is only about 7mA at full speed and brightness and much less at lower speeds and reduced brightness.
The 74HC14 Schmitt trigger IC draws very little current at 3V and less. I figured wrongly that since it is Cmos and its outputs switch very quickly, it would never draw much current.

Now I measured a supply current of 1.6mA for each oscillator at 6V. I discovered that the 74HC14's input Mosfet draws the current while it is a linear device following the timing capacitor's voltage.
A regular Cmos Schmitt trigger IC such as a 4584 draws only 20uA while its input is linear, at 5V. But its output current is way too low to drive LEDs. So I'll use a 4584 (or 74C14, same thing) for the 4V to 6V oscillators and another transistor to drive the LEDs.
Problem solved. I was afraid that I would have to put an off switch on the thingy. ;D

I discovered how to make it even brighter by removing a resistor on its PWM brightness oscillator! I'll let you know how it works out soon. ;D

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Hi Guys,
It works perfectly!
My "6V" green ultra-bright LED Chaser is brighter than before and draws only 250uA from the battery between flashes and with the brightness turned down.

I replaced the 74HC14 hex Schmitt inverters IC that draws too much current at 4V to 6V with a 4584 (same as a 74C14) ordinary Cmos IC. Instead of using another transistor to boost its output current, I used a "mickey mouse" diode as a gate so the 30ms pulses from the master "speed" oscillator gates the PWM "brightness" oscillator.

I changed the brightness pot wiring to an "Ante's Special " type of wiring with diodes at each end and the inverter's output feeding the slider. Now the PWM brightness range is from almost zero (with all my lights off I could barely see the skinny pulses on my 'scope) to very close to 100%.

I'll modify my last remaining blue ultra-bright chaser the same way then MAKE A MOVIE for you guys to see and hear me singing (croak!) and all my blinkin' LEDs all around!

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Hi Guys,
Correction: A 4584 IC isn't the same as a 74C14, and neither are the same for an oscillator's timing as a 74HC14 that is used in the 3V LED Chaser project.

Since the 74HC14 drew too much supply current for the oscillators with a 6V supply, I wanted to use an ordinary Cmos hex Schmitt trigger IC that draws much less current. The 4584 IC that I tried made the speed oscillator run too fast, so I increased its timing capacitors, C3 and C4, from the original total value of 800nF to 1.47uF, and it is still rather fast. I don't want to make the caps even bigger 'cause those metalized-film ones are big and expensive.

So I researched the hysteresis for all the Cmos hex Schmitt trigger ICs with a 5V supply:
- 74HC14 0.6V to 1.7V (original)
- 4584 0.25 to 1.0V (much less)
- 74C14 1.0 to 3.6V (much more)
- 40106 0.3 to 2.0V (too much variation)

The 74C14 is a good choice and the caps can be reduced to just one 330nF or 470nF one. The 4584 can be used, like I did, but the caps should be increased to a total of about 2uF.

I might post a separate project for a "6V Ultra-Bright LED Chaser".

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Hi Ante,
My original 3V LED Chaser project works fine.
I made a number of changes so it could use 3.2V to 3.5V ultra-bright green, blue or white LEDs, and a 6V battery. The changes are numerous so I'll post it as a new project.

I modified a 3V circuit with all the changes for the 6V circuit except it kept the original timing caps and the 74HC14 that works well with a supply down to 2V or less. I have it running beside an original one right now and they look and operate the same.

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Hi Guys,
I was wondering why my original 3V LED Chaser project looks as bright as the new circuit I designed for ultra-bright LEDs and a 6V battery. The original circuit produces 15mA current pulses in its LEDs but the effective current is reduced to about 10.5mA by the max duty-cycle limit of 70 percent by its PWM brightness control. The new circuit has an effective LED current of 15mA because its "Ante's Special" PWM control can reach 100 percent duty cycle.

My first "6V" ultra-bright chaser had 24mA current pulses that were reduced to about 17mA by its original PWM circuit. The improved PWM control allows the full 24mA and it looks much brighter.

I tried reducing yhe value of the LED current limiting resistor in the original and modified 3V chasers to make them brighter and the LED current didn't increase! The 74HC4017 must be at its current limit with a supply of only 3V and must be current-limiting.

The 3V chaser's LED current (and brightness intensity) increase from 10.5mA to 15mA is a 43 percent increase which must be negligible since our vision's response to brightness is logarithmic. But the 6V ultra-bright chaser's same percentage increase in current probably overloaded my vision and created a sensation of increased brightness. They are extremely bright.

I will build all chasers from now on with the new circuit. I have a new idea of using a spare inverter to gate the chaser off for a short sleep after a few revolutions. It will double the battery's life and look more interesting. I will post my 6V ultra-bright circuit as a new project with a parts list and description. Its schematic is here:

post-1706-14279142023306_thumb.jpg

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You will notice that a new capacitor has been added at the transistor. It is used to attenuate extremely narrow PWM pulses at minimum brightness. Both the original 3V circuit and the new 6V circuit need it when using ultra-bright LEDs, because they are so bright.
You should see the new 1.8V orange ultra-bright LEDs I found!

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Hey everyone. Im 17 and new to electronics and this is going to be my first real project. I play guitar in a band and I want to install this project in my guitar under the strings, and between the pickups for a little added stage wowing. Here is a picture of a guitar similar to the one I want ot put this in.-->1003_md.jpg As I said I want to put it between the two pickups(2" gap), under the strings. I planned on making a back cavity (for those who don't know what that is, it's this)-->12%20feb%2003%206%20b.jpg to house the project, and drill holes for the LEDs and pots. Question #1 is, Where can I get all the parts to make this project? #2 Will the project make a hum or buzz in my sound? #3 Any advice? Thanks to any and all responses.

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Hi Ibernez,
Welcome to our forum.
I have been making lots of these chasers. I have made some with Ultra-Bright LEDs, and they are really bright, probably more suitable for your guitar project. The Ultra-Bright LEDs need more than 3V so I modified the circuit a bit and use 4 AA alkaline battery cells. I'll post the modified circuit soon as an 6V Ultra-Bright LED Chaser project.
You might have a whine and a buzz in the guitar's sound if the project is mounted so close to the strings and pickups. I suggest mounting the circuit and its LEDs around the bottom edge of the guitar, to avoid interference with its sound and the LEDs would be seen better away from your "strumming" hand anyway.

Since you have AOL you are probably in North America, like me. I buy my stuff on-line from www.newarkinone.com or www.digikey.com since they have almost everything in stock and have pretty good prices. You pay online with a credit card and delivery is by courier the next day.

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Thanks for the advice. Im looking forward to the 6V Ultra-Bright LED Chaser. I figured the LEDs would make some kind of hum. The thing is is this is what us guitarists call a "project guitar". It's all hot-rodded with special pickups and stuff. I have broken pieces of mirror all over it and the only parts that aren't covered are the area under the strings and below the two pickups. So I guess I'll put it on the lower horn. Also, I forgot to ask, I'd like to put a on/off push switch in to turn it on and off. Maybe when you make the new mod circuit, you could tell what kind and where to put that in? Thanks.

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Hi Ibernez,
I just finished another 3V LED Chaser. This time I used orange Ultra-Bright low-voltage LEDs and they are really bright on-axis. I also used most of the changes that are in my 6V chasers.
I added another trick to this one and probably all future chasers: the LEDs chase around and around a few times then they go dark for a few seconds, saving the battery power, then start chasing again. ;D

A chaser would look cool in your guitar. Maybe it won't cause interference if you mounted the circuit and LEDs inside a metal box positioned under the strings.

An on-off switch can be wired in series with one of the battery's wires.

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So I can use Ultrabright Low voltage LEDs? that would be great because the smaller the cavity the better. I can get copper shielding tape like this shieldtape.jpg to put in the cavity. Do you think it could work under the strings with that? I think ill use the regular chaser project you made before. So can I use the "3V LED Chaser" project and just substitute with ultrabright low voltage LEDs?

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Hi Ibernez,
The low-voltage orange Ultra-Bright LEDs I found were in a bag marked "RED" and are "no-name-brand" from China or India. They measure about 1.8V at 20mA. They have a clear package and make a blinding light beam about 20 degrees narrow. Red and orange Ultra-Bright LEDs are usually 1.8V to 2.2V and will work fine in my original 3V Chaser project.
Blue, green and white Ultra-Bright LEDs are usually 3.2V to 5V and need a 6V circuit.

You have a good idea to use copper tape for a shield. Make sure to electrically join the pieces together and connect it with a wire to the negative battery terminal on the circuit board (ground). Maybe you can wrap the circuit inside the shield with insulating heavy plastic film to keep it from shorting to the copper tape. The battery doesn't need shielding.

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Okay, I should be able to find Red/Orange Ultra-Bright 1.8V/2.2V at 20mA on allelectroinics.com or something right? But whats all this about joining the shielding to the circuit? If it's not too much trouble, can you explain why I would have to do this?

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Hi Ibernez,
My orange LEDs are rated at 4000mcd brightness at 20mA and about a 20 degree total beam angle. They were about $5.00 for 10.

If you don't connect the shield to the circuit's ground, it will pickup the interference by capacitive-coupling due to its closeness and re-radiate the interference to your guitar strings and pickups.

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Hi Ibernez,
Those very bright LEDs are perfect. Just hope that their voltage is close to the low end of their spec so the battery will last longer.

Long ago, the "ground" connections of a radio were connected to a wire attached to a metal rod that was pushed deep into the earth. Today, the ground point of a circuit is just a common reference that all voltages are measured from. My schematic is marked showing a "ground icon":

post-1706-1427914204346_thumb.jpg

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So I just solder a wire from the copper tape to join the curcuit at the nearest place to the negative terminal? & By The Way, when you call for 1M Audio taper (logarithmic) potentiometer, is that the same thing as 1 Meg...etc.?

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Hi Ibernez,
All the ground points on the schematic should be joined together when you build it. The wire that you solder to the copper tape shield can be connected to any of those points.

A 1M (1 Meg) audio taper (logarithmic) pot is commonly used as a volume control in audio equipment. If you don't need a brightness control, replace the pot with a 1M resistor and the brightness will be maximum.

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Hi Guys,
I just finished a 3V LED Chaser using orange low-voltage Ultra-bright LEDs. It is extremely bright on-axis (the LEDs have a 20 degree beam). I used the new 6V circuit with a few changes to allow it to operate with a supply of only 2V to 3V.

My daughter leaves her chaser running all the time and was getting bored with it just going around and around and around and around and around and around and around and around and around and around, etc. (I was bored too) so I decided to spice up the circuit a bit by using its spare Schmitt-trigger inverters.
The new circuit rotates the LEDs for 3 revolutions then goes to sleep for a couple of seconds (conserving battery power), then starts going again and another sleep period, etc. Looks cool. I'll post the new circuit as a new project after I revise the Veroboard wiring to include the new features, and build a 6V one to make sure it works OK.

I just found out on Google that my new very inexpensive (I got a good deal at an after Christmas sale) computer is much better than its label and its advertisments. It has the latest Hyper-threading technology and an 800MHz front-side-buss! Woopee!

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