This is pretty close at 58cm wide, although only 10cm tall.
However, assuming board(s) will be mounted on something, why not use two (or more) pieces of veroboard? You could bolt/epoxy/solder some together.
Most PCB manufacturers can make you a board this size if that is an option.
The 60cm sounds about right for 2.54mm pitch, but how do you calculate 360 holes needed for 114 LEDs? (are they 3 leads?)
Things like a rough diagram of your intended setup, type of LEDs used, picture of VeeCAD layout might be helpful to find the best solution.
Any LED multiplexing solution will inherently reduce intensity of the LEDs pretty much linearly by the factor of the multiplexing duty cycle. This change in intensity is not identical to the change in intensity observed when current through the LED is reduced by changing series resistance: The resistance value is not directly the determining factor, the resultant current through the LED is, and that does not enjoy a linear relationship to resistance.
The human eye's perception of intensity of light, LED or otherwise, is far from linear: Intensity variations at low LED intensity, or for that matter in low ambient light conditions, are much more sharply perceived, than a similar change in intensity at a brighter point in the intensity curve, or under brighter ambient light conditions. This explains why the change in resistors did not show a significant change in perceived intensity.
To answer the specific question about over-driving LEDs: Yes, that is a standard mechanism for countering loss of intensity in multiplexed displays. To counter a 8-way multiplexed LED display's intensity drop, i.e. 12.5% duty cycle per LED, hypothetically the LED should be driven at 8 times the constant current. However, that is rarely practical, so either compromises must be made, or risks of LED damage must be accepted.
How much a given LED can be safely overdriven by, is (a) possibly specified in the datasheet, but (b) more typically determined by the display designer through empirical testing, especially in hobby and low-cost applications, if the datasheet-specified overdrive current is not sufficient, and risk of LED failure is acceptable.
- For more context on LED overdriving limits for pulsed load, see this answer.
- For a more detailed description of LED intensity and human perception, see this answer.
- Another answer in the same vein, with pretty graphs too.
Best Answer
(1) LED on times for phosphor LEDs are in the 100'2 of nanoseond range
(2) Turn on times for non-phosphor LEDs are typically in 10's of nanosecond range if driven correctly.
Average current = Peak_Current x time_on / ( time_on + time_off )
Peak current is assumed to be "steady".
(3) Brightness when mutiplexed
Where B_DC is the brightness when the LED is operated at this PEAK current when DC is used and k = a factor relating to loss of efficiency with current, change of efficincy with die temperature etc.
Initially k=1 is close enough.
or Brightness using average current =
(4) Modern phosphor LEDs have an allowable peak current 20% to 100% higher than the rated DC current.
ie you cannot usefully multiplex modern phosphor LEDs directly.
(5) SOME modern LEDs MAY allow higher peak/rated current ratios but
you should check the data sheet in EVERY case.
(6) There is a way to multiplex LEDs to allow high peak multiplex currents when the actual LEDS have low allowable peak/rated current ratios.
It takes more circuitry and/or design effort. Few people do this AFAIK
There are various possible implementations but the basic method is to multiplex power (LED drive) to an energy store and then drive the LED from the energy store in such a way that LED current is about constant.
An "energy store" can be a capacitor or an inductor, plus supporting circuitry.
(a) Multiplex into capacitor across LED directly. Input desired average current. LED will stabilise at appropriate voltage for the average current. Energy is lost in the driver due to unavoidable I^R loss.
Capacitor must be large enough to prevent LED current rising above rated value during recharge pulses.
The capacitor increases the turn off time to at least a few multiplex cycle periods and probably 5 to 10 multiplex cycle periods, and maybe much longer at very high multiplex ratios. Turn on time is under the control of the designed but will also usually be slowed to several mutiplex cycle times.
(b) Multiplex into eg inductor in series with LED to ground. Reverse diode from input to ground. This is effectively a buck converter.