LEDLabs can be assembled anyway which suits, however the lower profile components such as resistors, diodes etc would make it a little easier to assemble if soldered first. The PTC fuse or an axial quick blow fuse should be installed as no power is available without. The PTC is used for temporary short circuits or excessive short term current loads, an axial 1 amp fuse can be used, which would require replacing if blown., most usb power supplies also have current limiting protection.
The power supply requirements are generally a 5 volt usb rated @ 1 amp, usb battery power banks can drive LEDLabs, and are well suited. Powering from a usb battery or a computers usb port is the preferred method.
the stepper motor should be a general low power type like 5V 4-PHASE 28BYJ-48.
use a usb cable of good grade usb 3 no longer then 1M. As the voltage can degrade through the cable and cause the display to look dull, blue panel mount voltage meters are not recommended as they have a high volt drop for the leds inside them. Red voltage meters are the best suited as they have the lowest power requirements. Green and yellow coloured volt meters work well too.
The 1k potentiometers for the large led section, should be of good quality like bournes. (rs components code 488-5300) or similar quality.
The large led voltmeter has three connections on the under side of the pcb marked 0v +v and v-in, and are coloured silver, solder should be melted on these three points and the corresponding wires cut to about the correct length ensuring the red wire is soldered to v+ and black to 0v and the third colour usually white soldered to v-in.
Dot matrix displays and seven segment displays can be pushed into pin header connectors if required, this will allow for quick changing of the devices, for example changing the colour of the displays, no unsoldering is required if installed this way.
Care should be taken when soldering components to the board to ensure a good connection and not to leave the soldering iron on the board for to long, as a risk of burning the pads could occur. Also be careful when soldering 16mhz crystals as to much heat can make it fail, so if no programs on the atmega are working the 16mhz crystal should be changed.
Component identification and orientation should be observed as well, before soldering. The board shows component values like resistors and + and – symbols where necessary.
Note: When soldering the rightmost max7219 IC the bottom pin looks like it joins with another solder joint (this is because it does and if both solders flow together that’s okay, this is not a solder bridge.
The IC’s have dil sockets to solder in place first, then the legs of the new IC’s should be squeezed in to fit the socket. The dil resistors for the shift registers do not need sockets.
The large 1 watt leds should have a small length of wire soldered to the led connections where the + and – markings are, with the wire provided.
One module at a time can be built and then powered up to check it, this would be easier to locate a soldering error or component inserted incorrectly, than if the whole board was built then tested. The ptc fuse provided is now 800ma hold current 1 amp trip, this should be installed to allow power to the board, and should be suitable for most applications. A Higher value can be used to suit application type.
Several wire links are required and are marked accordingly.
Seven stand offs should be fitted where marked and forms the legs to the board.
Care should be taken when switching on any of the larger Leds as they are very bright when the variable brightness is set high and should avoid looking directly into them, always make sure the brightness is set low first. The 20R resistor can be changed to say a 100R to reduce further if required. The 20R reistor sets a current of around 110ma, and not there maximum range of 350ma which is to bright for this purpose. UV should not be looked directly into, as the peak wavelength can not be seen, just the visible side as in the purple colour.
The power supply requirements are generally a 5 volt usb rated @ 1 amp, usb battery power banks can drive LEDLabs, and are well suited.
Also a good quality usb cable should be used, a thick cable, cheaper cables can send the sensitive comparators of the Lm3914 into dot mode even when bar mode jumper switch is on. Usb 3 or good quality usb should be used to avoid problems.
LEDLabs can be connected straight from a laptop usb port, if it’s usb 3 which can source 900mA, usb 2 is about half this value, or the current drawn from a particular circuit is known, LedLabs in it’s Quiescent state, or generic applications on the board would allow connection to a computer usb port. The two boards in the videos on the main LEDLabs page are connected to one computers usb ports, however due to the rapid turning on and off of the devices, this load current is quite small.
if only using up to 300ma then it could be driven from various sources.
The large Leds on full brightness consume up to 110ma each, so when on constant, this would use 550ma for all 5 and around 100ma for other quiescent devices.
This is why a 1 amp is recommended, however other devices consume considerably less.
If no particular program is running on the dot matrix displays, it will just have random data loaded and may flash or light all segments when not in use, if the data in to the max7219 is taken to 0v, this should blank the display and save power. Also the 10k resistors near the dot matrix can be changed to a 27k or 33k, this will reduce brightness slightly but will be less demanding on the power supply.
Note:- if sourcing own components, and clear leds are chosen rather than the standard diffused types as (Led labs supplies) the resistor values may need to be increased as these are usually very bright, bread boarding these first to get the brightness required may be good to do first, A 10k resistor is usually bright enough for clear led types. a 1k is used on led labs for some standard diffused type leds.
The 4026 counter section has 330r resistors printed on silk screen, which gives a modest display brightness on both red and green 7 segments, and keeps within ohms law, however lower values can be used. (ie 10r or 100r) as the 4026 regulates the current anyway, and does not need resistors at 5v. this will acheive max brightness.
Lm3914 voltage scale is 0-3.6v, rather than 5v as silk screen states, on some of the pcb boards.
As the ldr and thermistor have thin wires, make sure they are not touching, to avoid possible problems.
Dot Matrix Displays are orientated with the code lettering towards the bottom of the board. If not using the display, to avoid floating pick up noise which may flash the display, the data in pin should be taken to 0v.
Further note: due to the very noisy max 7219 display drivers ic’s, which are renowned for generating noise on the power supply unit.
certain frequencies and switching of these chips can show noise radiated on the large led voltmeter, this only may happen on certain programs at given refresh rates. and gives an oscillating effect on the voltage meter.
this may also never arise depending on code sent to max7219 ic’s.
The other way is reducing the brightness to the dot matrix displays by increasing the resistor 2x 10k next to the displays to 27k will reduce the power consumed.