Hi All,

I'm building something where a single pushbutton will increment 8 white 5mm radial LED's. The idea is each time you press the button - it will illuminate an LED until you get to 9 presses, then it will reset. I'm looking for an IC like a lot like a decade counter, but each channel stays active on as it counts.


Does something like this exist?

 

A CD4017 lights only one LED at a time with 10 steps.

 

Hi All,

I'm building something where a single pushbutton will increment 8 white 5mm radial LED's. The idea is each time you press the button - it will illuminate an LED until you get to 9 presses, then it will reset. I'm looking for an IC like a lot like a decade counter, but each channel stays active on as it counts.


Does something like this exist?

10 different states creates some complexity if you want to do it all with hardware. If your up for writing a bit of code (or loading some code that someone here may write fire you into an Arduino module, that becomes very easy with a minimum amount of hardware.

 

A CD4017 lights only one LED at a time with 10 steps.

I understand. I'm just using a typical decade counter as an example. I'm looking for something that will illuminate each LED until the IC is reset - so think the same functionality as the CD4017, but each channel illuminates and stays illuminates until it's reset.

 

10 different states creates some complexity if you want to do it all with hardware. If your up for writing a bit of code (or loading some code that someone here may write fire you into an Arduino module, that becomes very easy with a minimum amount of hardware.

I'm not against the idea of using an Arduino, however I'm very space limited on where the completed unit is going to go.

 

why not state actual dimensions of available space? "space limited" tells us nothing.
are you looking for THT parts or SMD is fine too?
how would you like an 4017 for counter and an EEPROM as decoder? for example AT28C64B.

 

A simple low end CPLD would be one of the easier solutions and is space saving.

 

Have you looked at using a shift register? That should come close to what you seem to be trying to do. A bit of glue logic should close the gap. For the most part, just putting an inverter to pass an inverted version of the final output back to the input might be all you need (plus a way to ensure that it initializes in the all-zero state). This will not have the automatic reset behavior you are describing, but that's just a bit of glue logic again.

 

a Johnson counter comes to mind... easy to put together using 74LS273 or similar. convenient pinout too

 

- Connecting Q1-Q8 outputs of a 4017 to Corresponding D-Type flip-flops, and
- The Q9 output to the reset of the 4017 and the reset of all of D-type flip flops.
do not connect Q0 to anything to allow all LEDs to be shown as off.
- in the following GIF, the reset of the flip flops is active high but many real chips reset on active low so you'll need to invert the signal from the cd4017 Q9 pin.

(Note - the gif was compressed and one button press doesn't show but the LED lights)

You can pick your Flip flop. Make sure it interfaces with a CD4017 and that they have enough drive current to directly power your LED.

finally, you'll need some resistors and capacitors to debounce your button to make sure it sends only a single up transition to the CD4017 instead of a noisy multiple-bounce mess.

 

Here's the LTspice sim of a circuit with two IC's, using the 74HC164 shift-register that should do want you want.
A 74HC74 flip-flop is used to generate a short reset signal when the device is clocked after the output 7 goes high.
The other FF in the package is used to suppress the mechanical switch bounce by providing about 70ms of delay before CP can go back low, independent of what the switch is doing, while generating the fast clock rise and fall times required by the shift-register.

The SR can source or sink 4mA to drive the LEDs directly.
Edit: Modified design to simplify the reset circuit.

 

A 4017 running at the maximum 18V, and using red LEDs might just do it:
Put the LEDs in series, and join each output to the string of LEDs with a diode. Diagram later if you need it.

 

A 4017 running at the maximum 18V, and using red LEDs might just do it:
Put the LEDs in series, and join each output to the string of LEDs with a diode. Diagram later if you need it.

A diode and a resistor. Each output will be driving a different number of LEDs with the same voltage, so each stage will need a different current limiting resistor.

By the time you have the diode drop, there's very little overhead left for that last output that's driving eight LEDs. If the Vf averages out to 2.2 V, your goose is pretty well cooked.

And this is assuming that the part can maintain the output at the rail even under load, and that it can drive the LEDs in the first place. I'm a bit skeptical of both.

https://www.ti.com/lit/ds/symlink/cd4017b.pdf



At 15 V supply rails, the device is only spec'ed to source of sink 3.5 mA (about twice that being typical) when the output is pulled 1.5 V away from the rail. So even if you use a Schottky diode, you may well be down to just over 16 V even if you choose LEDs that only want 5 mA or so.

 

I'm building something where a single pushbutton will increment 8 white 5mm radial LED's.

What is the supply voltage, current you want to operate the LEDs at, and their nominal forward voltage?

 

Does something like this exist?

Have you ever considered a Pic-Micro?
Would be a piece of cake with one.

 

You could do it with one of the LED voltmeter ICs in the bar mode, plus a charge pump so that each press dumps more charge into the capacitor. Then the last press drives an FET that drains the cap back to zero. That could be done with one IC, I am thinking. And a couple of transistors. About as small as I can come up with, no code to generate and almost no digital logic.
For only 8 LEDs, use a 4017 with resistors to deliver higher voltages and then the last one to deliver none, and reset to zero.
That takes only 2 IC devices and tiny resistors, no capacitors, and the bar-graph IC drives the LEDS directly. That is as simple as I can make it.

 

Here's a version using a 4017 and SCRs to the latch the LEDs.
EDITED, from crutschow's suggestion in post #18 and #26 (R3)

 

Here's a version using a 4017 and SCRs to the latch the LEDs.

Since the 4017 has a Schmitt-trigger clock input, you could debounce the switch directly at the input and eliminate Q1.

 

Since the 4017 has a Schmitt-trigger clock input, you could debounce the switch directly at the input and eliminate Q1.

I did not though that, thanks. See EDIT on post #17.,

 

Here's my LTspice sim of sghioto's circuit.
I modified it slightly to get the correct timing for the reset at the 9th button press.