– Download as PDF File .pdf), Text File .txt ) or read online. Electronic theory, schematic circuits and PIC tutorials. Like other multiplexing techniques (eg matrix), charlieplexing is used to control more loads The two LEDs are connected anti-parallel, the anode of the red LED (left) is. The term “Charileplexing” is not a familiar one for many electronics hobbyists. Charlieplexing is a technique proposed in early by Charlie Allen (at.

Author: Nikolkis Migami
Country: Malta
Language: English (Spanish)
Genre: Health and Food
Published (Last): 4 September 2011
Pages: 283
PDF File Size: 3.19 Mb
ePub File Size: 14.21 Mb
ISBN: 282-2-43335-250-3
Downloads: 12408
Price: Free* [*Free Regsitration Required]
Uploader: Faebar

Only one LED terminal goes to a resistor, choose either cathode or anode, the opposite pin of the LED; the one not connected through a resistor; will be the “strobe” that is powered whilst however many up to three of the LEDs connected to that charlieplexibg are lit at a time.

The method uses the tri-state logic capabilities of microcontrollers in order to gain efficiency over traditional multiplexing. If dungeon crawlers with satisfying hardware are more your thing, you really need to check out Twang. By using our website and services, you expressly agree to the placement of our performance, functionality and advertising cookies. If for example the rate is 10Hz, the flickering will be visible.


Charlieplexing with LED dot matrix modules. Typically, LEDs operate from 2. The pictures change so fast, that the human eye thinks it is a continuous film. A balance between complexity and pin use can be achieved by Charlieplexing several pre-built multiplexed LED arrays together.

By using tri-state logic, the matrix can theoretically be expanded to any size, as long as pins are available. All the outputs used to drive a Charlieplexed display must be tristate.

The Charlieplexing

Because the circuit in this LED is same as the diagram you state in this page. Thanks guys for carlieplexing replies First, though you’re right to say that in this case the speed gain from direct port manipulation is not appreciable, it still has merit, in that directly setting the port direction registers ensures that the tri-state outputs are changed exactly simultaneously.


Typically 7-segment displays are made to have a common cathode, sometimes gheory common anode, but without loss of generality suppose it is a common cathode. Charlie Allen originally championed this technique internally at Maxim, and so the shorthand name “Charlieplexing” came into use to distinguish reduced pin count multiplexing from the traditional method.

Charlieplexing 8 LEDs – trouble generalizing routine

Drawing inspiration from Charlieplexing, he came up with the idea to connect things in such a way that gheory node is connected by one connection to every other node — a complete graph from a topological view point this makes so much more sense visually.

It is impossible to get 56 bits of information directly from 8 trits the term for a base-3 character, as the pins are 3-state of information, as 8 trits fundamentally comprises 8 log 2 3, or about I suppose you can go to higher frequencies, maybe higher than Hz.

They may consume very little current, but they will not light if the voltage across them is bellow a specific value. If you connect for example the LED in Q1 and Q2 and Q1 becomes 1 whenever Q2 becomes 0 and vice versa, and this is done very fast, then the effect that you would see is both LEDs light.

All LEDs in all 8 7-segment displays cannot be turned on simultaneously in any desired combination using Charlieplexing. During this state, the port’s internal resistance gets very high values Mega Ohmand the current that flows through the port is very small, measured in micro amperes. What this means is that unlike most methods in which the loss of a single LED merely causes a single burned-out segment, when Charlieplexing is used, one or two burned-out LEDs, whatever the mode of failure, will almost certainly cause a catastrophic cascade of unintended lightings of the LEDs that still work, very likely rendering the entire device completely and immediately unusable.


You will see that the LED will not appear having both colors light. To read whether a switch is open or closed, the microcontroller configures one pin as an input with an internal pull-up resistor.

Same applies of course if we try to light L2. The solution is to connect one resistor for each LED, like this:. If the problem is a short between nodes x and ythen every time any LED U with either x or y as its anode or cathode and some node z as its other electrode is supposed to come on without loss of generality, suppose U’ s cathode is connected to xthe LED V with cathode y and anode z will light as well, so any time EITHER node x or y is activated as an anode OR a cathode, two LEDs will come on instead of one.

By using this site, you agree to the Terms of Use and Privacy Policy. The action begins with the next button press.


A third GPIO is used as a touch button input. If you need to drive more than 7 mA per LED i.

You can calculate the maximum number of LEDs that can be controlled with Charlieplexing, if you solve the following formula:. Is higher frequency eg Hz not allowed in Charlieplexing? At 8 April5: