Multiplexing is achieved by setting each of the 7 Arduino outputs to OUTPUT/HIGH in turn for a short period, in each case having set up the other 6 as either OUTPUT/LOW or INPUT. Hence 1:7 multiplex ratio.

Bar driverwindows 10

The LEDs are organised into 7 groups of 6 (except that last group that has only 4). Each group's common anode is energised when one of the 7 Arduino outputs is set to OUTPUT/HIGH, switching on the NPN (which is wired as an emitter-follower so needs no base resistor). The cathodes of the group are wired to the other 6 Arduino outputs (via current limiting resistor). If these other 6 outputs are OUTPUT/LOW, the LED lights up. If they are INPUT, the LED does not light.

dot/bar displaydriveric

Actually it appears space is going to limit me to only 1 block each side :(. I think 8 leds will give an easier read than a moving dot. The voltage will have to read only 10 to 15volt range

As for measuring your voltage and current, use the Arduino' internal voltage reference (1.024V on Uno but 2.048V on Lenonardo for example). You can directly measure the voltage across the shunt, and for the voltage, use a divider made from a 10K and 510R which should bring your 12V down to around 0.6V also.

Use our cigarette butt calculator to estimate how many butts your business needs to dispose of so you can order the right bin for your needs.

For each block of 20 leds, do you want one led to light up indicating the reading? Or a line of leds? In other words if the reading is 75% of maximum, do you want just led #15 to light, or leds 1 to 15? If the answer is just one led, there is an easier way and you will not need the max7219/21. If the answer is 15 leds, it can still be done with a few transistors instead of the max7219/21, but it may be easier with the max7219/21.

dot/bar displaydriver

Hi all I want to driver a pair of 20 block LEDs, each on a different analog task hopefully from the same arduino. Is a Max7221 suitable to drive each block?

Stop by one of our visitor centres or look for one of our city ambassadors for advice on things to do, places to eat, or the best attractions to visit.

Personal ashtrays are designed to fit in your pocket or handbag. They encourage smokers to take personal responsibility for their waste.

Most appropriate for outdoor café and restaurant environments, enclosed windproof ashtrays provide diners with a table-top alternative to dropping their butts on the ground.

For each block of 20 leds, do you want one led to light up indicating the reading? Or a line of leds? In other words if the reading is 75% of maximum, do you want just led #15 to light, or leds 1 to 15? If the answer is just one led, there is an easier way and you will not need the max7219/21. If the answer is 15 leds, it can still be done with a few transistors instead of the max7219/21, but it may be easier with the max7219/21.

BarDiver Cocktails

Hi guys, I'm going to back track a bit and say that with some butchery I can indeed fit 20 segments high. But i think folks would appreciate 10 and 20 segment options. I guess i just don't like the look of LCD's.

I intended to use Kingbright's DC-10SGWA stacked one over the other. One pair to do voltage up to 14v DC and the other pair current (DC) for my 4 wheeled crate. The current by voltage across a 0.01ohm shunt in a 12.5v(norm) 60A(max), that should give me 0.6v max across the shunt. The voltage take between a pair of 1Mohm resistors. LM3914's are the other option but I don't know how to make the arduino output in the 0-5v range or if PWM can accomplish that.

We accept the invitation in the Uluru Statement from the Heart and are committed to walking together to build a better future.

El Malo

These ashtrays feature butting-out surfaces with holes for cigarette disposal. They can be placed at any desired height and can be easily relocated to where smokers congregate.

I'm not seriously suggesting Andy chooses that design. With that many LEDs, max7219/21 would be easier. But I just wanted to show its possible.

Bardiver yelp

We acknowledge and honour the unbroken spiritual, cultural and political connection they have maintained to this unique place for more than 2000 generations.

Depends on how the block is wired internally. MAX7219/7221 expect to have groups of 8 LEDs with a common cathode per group, and the anodes from each group connected (As, Bs, Cs, etc) in common.

The City of Melbourne provides street litter bins, many of which have a butt-out surface on the top. Smokers are encouraged to grind out their butt on the surface at the top of the bin and then place the butt inside the bin. This stops lit butts creating fires in the bins and reduces the risk of butts being blown away to create more litter.

You could also consider using a 16x2 lcd display. These are cheap, easy to connect to Arduino and can display numbers as well as a bar graph. For example

The City of Melbourne respectfully acknowledges the Traditional Owners of the land we govern, the Wurundjeri Woi-wurrung and Bunurong / Boon Wurrung peoples of the Kulin and pays respect to their Elders past and present.

But that's getting a bit complicated for a beginner, and we don't know if the other pins are needed for anything! Hence the original, simpler-to-understand-and-code version before.

Freestanding ashtrays provide a safe and cost-effective way of collecting cigarette litter. Many can also double as bollards.

Bar driverdownload

Are you looking for an LED Bar Graph Array thats perfect for level indicator applications? Contact Kingbright to learn more about our selection of bar graph LEDs.

CharBar

Up to two-thirds of all cigarette butts are discarded on roads, footpaths and green spaces. Most end up in Melbourne’s waterways, making up about one-third of the one billion items of litter entering our waterways each year. Cigarette filters are made of cellulose acetate, a non-biodegradable plastic which leach chemicals in soil and water that becomes toxic to marine life.

Businesses have a legal responsibility to manage the litter generated by their business. This includes disposing of the cigarette butts littered by staff and visitors to your business, even if they are dropped outside your property boundary.

Information on The Environment Local Law, Activities Local Law and the Melbourne Parks and Gardens (Joint Trustee Reserves) Regulations 1994.

So let the Arduino multiplex the LEDs as a rising bar. That works too, as long as all the IO is available. Could do it a 4 groups of 5 also, use 9 pins.

Providing appropriate butt litter bins for your business is one way to make it easy for people to dispose of their butts properly and to meet your legal responsibilities. Once the bins are installed, it is essential that they are regularly emptied and cleaned so they operate efficiently.

If you are down to 2 x 10 led bars, max7219 seems overkill. I would drive directly with 10 digital outputs to drive the anodes of both bars, (via 10 ~330R series resistors) plus 2 digital outputs to drive 2 npn transistors (eg. Bc337, with ~4K7 base resistors) for the common cathodes.

Ok, 10 discrete LEDs. Using 2, 20 discrete LEDs. Connect them up in groups of 8 with a common cathode, treat them as 3 digits with MAX7219. Bits of digit0 drive the first 8, digit1 the 2nd 8, digit2 the last 4.