So a fade effect something like in this video?

Fader Effect

Should the fade up start on the next sequential LED as you start the fade down on the current LED to help the illusion of the beam moving?

That might be a relatively simple application for a little 8-pin PIC micro controller (like the circuit below but no transistors and with just four LEDs connected to the GP0, 1, 2, and 4 pins).

 

I have a cheap Chinese MOOD LIGHT I bought for a low price at Wal-art.
OOPs. Did I say Wall-Fart? Wall-Chart? I mean Wal-Mart.

It probably uses a digital part to do the dimming and brightening because it has obvious steps of current. Its brightness goes JERK, JERK, JERK, JERK up then JERK, JERK, JERK, JERK down.

Real analog circuits smoothly dim and brighten the LEDs.

 

So a fade effect something like in this video?

Fader Effect

Should the fade up start on the next sequential LED as you start the fade down on the current LED to help the illusion of the beam moving?

That might be a relatively simple application for a little 8-pin PIC micro controller (like the circuit below but no transistors and with just four LEDs connected to the GP0, 1, 2, and 4 pins).

I don't recall fade being in the OPs specs. I am close to moving this post as a hijack.

I actually do cover fading in my article. There are several ways to do it, all of them work.

 

I don't recall fade being in the OPs specs. I am close to moving this post as a hijack.

Just checked... You're right... The OP didn't mention it... I must have assumed smooth fading would be necessary to simulate movement of the light beam... My apologies...

Regards, Mike

 

Hi

I was just checking in to see how the circuit redrawing is coming as mentioned in Post # 20?

Thanks Again for All your help.

George

 

The weekend cometh. Sleep, draw,sleep, eat...

 

OK, first drafts. If you have any questions ask. If you want to go surface mount, ask, it would be much smaller. A 4017 could be used instead. but these parts are much more common. I just looked at the datasheet for a 4022, I was wrong about the number of pins, but the pinout is slightly different than a 4017. I would be willing to redraw this if needed.

 

Hi Bill,
Your first circuit has a single current-limiting resistor for four LEDs.
When one output lights a 2.2V yellow LED then the other LEDs have a reverse voltage of about 9V across them which exceeds their maximum allowed reverse voltage of only 5V.

 

I thought about putting the resistor in line with Vcc. It is still doable I suppose.

 

I thought about putting the resistor in line with Vcc. It is still doable I suppose.

Then the supply voltage for the IC will bounce up and down and its clock input might not work.

 

You might have to throw a signal diode on each line to protect the LEDs and reduce R4 accordingly. You've got plenty of voltage headroom to do it; that was what started the problem.

 

Then the supply voltage for the IC will bounce up and down and its clock input might not work.

No, think about it, each LED will be the same, and an LED will always be on. The transients as it switches between each output will be very short duration indeed, and should be handled by the caps.

The idea is as low a count part as possible. It could also be a zener instead of a resistor inline with Vcc to eliminate the current limiting resistors all together.

 

Hello again

Thanks for the updated circuit But a question, in Post #27 what is the value of Q1 -- Q4 and there is No mention of the circuit working on Vcc + 7.2v, can it? You show it twice at 6v, and once at 12v, so I guess 7.2v should be o.k? I just want to make sure.
Also if its` not too much trouble I would like to see a SMD circuit diagram as well please.

Thanks again for your help.

George

 

All you need for 7.2VDC is a minor tweak on the resistor value. I'll draw up a 4017 circuit next. As for transistor value, if you go through my article NPN's can be 2N2222A and PNP 2N2907A, or their plastic equivalents (PN2222A and PN2907A).

 

Hello,

I was wondering how that circuit redraw; Post 34, was going?
Is it possible to use yello SMD LED`s in place of the 3mm yellow LED`s. I was just wondering ahead for the future. I`m Good with the regular 3mm LED`s for now.

Thanks Agian for All the help.

George

 

Surface mt & 3mm should act the same. As to 7.2 V ,' would use 220Ω's, direct drive fron 4017. With 8.5V, 6 old AA cells. Yellow, 5mm LED. 680Ω= 1.85V, 7.6 mA; 470= 1.87V, 9.1 mA; 330= 1.89V, 10mA; 220= 1.95V, 12.7mA; 150= 1.955, 14mA; 100= 1.96, 14.7mA; 68= 1.97V, 15.2mA; 0= 1.99V, 15.9mA. Could detect only slight dimming from 15.6mA down to 12.7mA; bigger change from 12.7 to 10mA. No heat detected.

 

Saw this SM yellow, 120 deg, 2V @ 20mA LED by Everlight # 67-21VYC/TR8, stocked by Electronic Goldmine # G17053.

 

Electronic Goldmine sells SURPLUS stuff that might be No Name Brand (who is Everlight?), factory rejects or obsolete things.
Is there a detailed datasheet for the LED?

 

It is funny, until I hit this website I had never seen a data sheet on a LED. Even now it is rare.

Some components it is absolutely necessary, but with LEDs?

 

It is funny, until I hit this website I had never seen a data sheet on a LED. Even now it is rare.

Some components it is absolutely necessary, but with LEDs?

I bought a bag of bright wide angle Fairchild red diffused LEDs. The datasheet is very detailed. It says the forward voltage at 20mA is from 1.5V to 2.4V with 1.7V being typical.
All of my LEDs have are the same colour, brightness and angle. Their forward voltage at 20mA are almost the same at 1.8V.

I was given many Philips Luxeon SuperFlux LEDs for helping a guy on a website. They have 4 pins and a very wide angle. Their max allowed current is 70mA. I made a night light with 36LEDs at 55mA each and it lights my entire neighbourhood. Another night light has 16 LEDs and it is bright but not too bright.