LED Chaser VU Meter style

[darryl_co]

Hi,
I want to build a 10 LED chaser VU meter style.I used the IC CD4017 but that is not what I am looking for.My requirement is that the LEds light sequentially without switching off the previous ones like a VU meter but operating with a external or internal clock pulse.To elaborate more The LED 1 lights than LED 1 & 2,then 1,2&3, then 1,2,3 & 4 .......,1,2,3,4,5,6,7,8,9 & 10 and so on.
Please guide and help me.What circuit or IC do I use?

 

[alec_t]

The LM3914 (linear response) or LM3915 (logarithmic response) is what you're looking for.

 

[darryl_co]

Yes somewhat like the 3914 but not exactly.The 3914 would light leds starting from 1 upto the 10th led but than start switching of from the led 10 down to 1.I need 1 to 10 then again 1 to 10,always the same start and the same end.Also as the 3914 and 3915 ICs are very old components they are very costly around my place in India

 

[alec_t]

The 3914 would light leds starting from 1 upto the 10th led but then start switching off from the led 10 down to 1

Not if you fed it with a sawtooth wave (i.e. voltage ramps up then drops abruptly). If you're concerned about cost then I can't think of any cheaper way than using a 3914 to do it.

 

[audioguru]

I bought some brand new LM3915 ICs for $1.00 Canadian each from a surplus parts store. That is only 54 Indian Rupees.

 

[rikilshah]

May be you could use 74HC595 SIPO registers, in case you are comfortable with Microncontrollers. They are pretty nice and will give you freedom of controlling more number of LEDs with small amount of control pins.

Arduino has very good libraries for the same.

 

[transistor495]

Yes somewhat like the 3914 but not exactly.The 3914 would light leds starting from 1 upto the 10th led but than start switching of from the led 10 down to 1.I need 1 to 10 then again 1 to 10,always the same start and the same end.Also as the 3914 and 3915 ICs are very old components they are very costly around my place in India

That is a ******** chaser.

When 10 Led's are lit then if it wants a start then you need to reset the whole thing. This is a pakka PIC application. Google 'led chaser using pic' and start from there.

 

[jbeng]

You could try a circuit similar to this one. As you can see, the sequence generator is a 4017 counter and the LED drivers are ULN2003A darlington arrays. All you need to add is a clock generator circuit. For the steering diodes, use schottky barrier diodes, as they have low forward voltage drop. Select the LED current limiting resistors based upon your supply voltage.

Edit: Dead thumbnail link removed - see my reply on Jan 13, 2013 for schematic

 

[darryl_co]

Sorry jbeng I cannot see the thumbnail of your circuit!

 

[darryl_co]

Searching Google for "led chaser using pic" gives me results of one led at a time,I need a bar array of leds to light at a time,The LED 1 lights than LED 1 & 2,then 1,2&3, then 1,2,3 & 4 .......,1,2,3,4,5,6,7,8,9 & 10 and so on not first 1 than 2 than 3 than 4 and so on

 

[audioguru]

I have LED chasers that chase around 5 times then stop for a pause. Then chase around and pause again, over and over. The ones with RED, orange and yellow LEDs use two AA alkaline battery cells (3V droppping to 1.7V) that last for 6 months. The one with blue or bright green LEDs need more voltage so they use four AA alkaline battery cells (6V dropping to 3.5V) that last for 6 months. The LEDs are driven at 24mA by a 74HC4017 so they are very bright. Each LED blinks on for only 30ms so the battery lasts a long time.

Beside my chasers I have an LED VU meter in the bar mode. It is also very bright but is powered by a wall-wart or its rechargeable 9V Ni-MH battery.

 

[jbeng]

Must have been a casualty of the server hard drive crash...

Edit: Dead thumbnail link removed

 

[darryl_co]

jbeng - Unfortunately no.I am unable find or click to view the thumbnail

 

[Blueteeth]

Maybe I'm just odd but seems you guys are either pushing for a PIC, or not getting what the OP wants. I believe he/she wants a 'bar' of LED's to travel, say 4 LED's on, moving from left to right. But perhaps with 10 LED's, and a bar of 10 LED's wide. So ultimately its a bargraph that 'fills up' from left to right, then 'unfills' from left to right (which is the same sequence as the first, but all bits inverted). Can easily be done with a few TTL/CMOS logic chips. A shift register for example, with its serial output, inverted, and sent to the input. That would have the limitation that the number of LED's would have to be the same as the shift regsiter (8, or 16 for two cascaded shift regs).

An unbuffered shift register like the 74HC164 would do that just fine. The 74HC595 would require loading the shift register contents to output buffer every time (could be done on the falling edge of the clock).

The main disadvantage of using pure logic, as opposed to a microcontroller is, the sequence is really down to hardware, and so, is fixed - where-as microcontrollers, can do many different sequences, just a question of software.

How many LED's are we talking here? and how many LED's are to be lit at any given time? let me know and I'll knock up a schem

 

[schmitt trigger]

There are many ways to skin a cat...
You could go the discrete-function digital way.
You could go a full fledged microcontroller, probably the best by the ease which one can change patterns and sequences.
Or you coulg go the analog way, using an LM3914 in bar mode, fed by a triangle wave.

 

[darryl_co]

Blueteeth- Good to find that you understood what I need, but just a small correction "So ultimately its a bargraph that 'fills up' from left to right, then 'unfills' completely and then refills up' from left to right "
"How many LED's are we talking here?" Its 10
"how many LED's are to be lit at any given time?" - 1 to 10 (+1 led for every clock pulse)

 

[Blueteeth]

Np man, its often very difficult to describe an idea using words alone, which is why diagrams are an enineers best friend Also, we see so many 'led display' questions, that the LM3914 gets called up to service very often because it can do the 'solid bar graph' thing really rather well - and allows those who aren't up on digital/microcontroller electronics to build a relatively simple circuit with easily obtainable parts.

I'll post a quick schematic later, I can't guaratee it'll completely do what you want, but would be a good start to 'tinker' with a circuit. Also, if y're ordering parts for this, you could knock up another display for a single LED on at any given time (I know thats not what you're after, but the knightrider thing is a common one) with a 4017. I'm afriad I haveno idea what level yo're at with electronics, so apologies if we get too complaited, or patronise you.

- BT

 

[Blueteeth]

Ok, here's something I just knocked up. I can't guarantee it'll do exactly what you imagined, but I'm pretty sure it'll at least be close. You could also expand it for more LED's (up to 16 using two shift registers) or reduce it down to 8 (one shift register). You could also change how many of the LED's that are 'always 'on', but changing the feedback from to the transistor.

Quick explanation:

The inputs to the shift register at the top, are A and B, these are tied together, although they are AND'd so you could tie A to VCC (+5v) and just have B as the input.

On power up, R3 and C1 make sure that the registers are '0' - so all LED's are off. The 555 timer is configured as astable and provides a 4.8Hz clock to the shift registers. Every low-to-high transition, the shift register takes the input from AB and moves it to the next register, as 'QB' output on the second shift register is 0 (after power up), the input to the transistor is 0, so its collector is at 5V - the input to the first shift register, so this lights up the first LED on the first clock pulse. With each pulse the LED's light up until after 10 pulses, they are all lit - at which point, QB on the second shift register is '1', so the transistor is turned on, pulling the input to the first shift register low. So on the 11'th pulse, the first LED will turn off, then the second, then third etc.. until finally all LED's are off again, at which point the process starts again.

By changing which shift register output goes to the transistor, you can change how many LED's are lit at any given time... so, say you wanted a line of 6 LED's to be lit, moving across the display, then the input to this transistor will be the first shift-register QF.

Just to complete it I've added a regulator circuit.

Note this will only scan the LEDs one way.

Any criticisms welcome, its just a quick 15-minute rough draft. I've kept the resistor and capacitor values mostly the same for convenience (10uF, 10k, 220ohm, 100nF). changing R14 and R15 will change the speed of the clock, so you could replace one of these with a potentiometer for control.

 

[schmitt trigger]

Brilliant!
No pun intended

 

[Blueteeth]

Just realized a couple of errors:

1. The chip number should really be '74HC164, dunno why I used AC, HC, or HCT would be just fine - with HC allowing you to power the circuit with 2 AA batteries.
2. The power connection to one of the shift registers is mislabeled as 'IC3', should be IC2 :/