Open Source Hardware

One of our values is to share what we learn by making our projects open sourced following the principles of Open Source Hardware with our partner in crime OpenFab.

Find our tutos in WikiFab and be welcome to contribute !


Open-source hardware means sharing the files needed to build *and* modify your hardware. As the open-source hardware definition explains, that means the version of the files that you would prefer for making changes to the design, not an intermediate or obfuscated version. For mechanical stuff, this means the original CAD files. For circuit boards, it’s the original schematic and board layout files.

XYZ knot


More information on the xyz

A good address for Alu in Brussels







Little battery module

*Little battery module* manuel
1. switch the battery on (middle) -> is the LED screen on ?
2. hook up generator bike (normal mains plug) -> do you feel resistance when pedaling ?
3. plug in the 3D printer (plug) or other device (USB) -> is the device powered ?
4. pedal to provide power (pedals) -> is the battery charge staying steady ?
(when in trouble, call)
– there is not enough power > check the gears of the bike
(in worst case, plug the charger in the regular 220V nuclear)
– the voltage limiter is triggered too often > pedal backward, use more power
(in worst case, unhook the voltage limiter and stay below 50V while generating, material needed : english key 10, multimeter)


top left : converter IN
top middel : busbar between IN – OUT – BATTERY
top right : converter OUT 24V
side left : OUT USB and diverse chargers
middel : BATTERY
side right : battery charger (220V nuclear to 28V)






left backside : bike generation power IN (normal mains plug)
left top : converter OUT (24Vout, 8A, 40Vmax, green LED)
left bottom : voltage limiter (4.7Ohm, 56Vsafety, red LED)
middel top : positive bus bar IN (80A diode) – BATTERY (to 10Asafety, LED screen)- OUT
middel bottom : negative bus bar
right : converter OUT (28Vout, USB, 20A, 55Vmax, blue LED)




left : positive to thyristor (40Amax) and zener (56Vtrigger)
right : thyristor to resistor (4.7Ohm, red LED) – resistor to negative bus bar
*when triggered, ask to pedal backwards before restarting generating on the bike*





Energy module


An electronic component able to hold a charge. It can be used in the same function as batteries with the following differences :
+ a capacitor is easier to recycle than most batteries (references will follow).
+ a capacitor can provide and absorb a higher peak power.
– the voltage varies with the charging state of the capacitor (it needs an additional converter to provide the voltage of the system)
– the energy by weight capacity is less interesting than with batteries.
– the cost by energy is higher.
– the lifetime is quasi infinite (1M cycles).

The energy storage of a supercapacitor :
energy = 1/2 * C * voltage difference^2
ex = 1/2 * 500F * (16-12)^2 = 4000J = 1.11Wh = 1 cyclist for 1min20sec



*Renewable energy – what can you expect ?*
_the numbers_
1 cyclist = 100W power generated during 5min
= 75W during 15min
= 50W during 1h
sound system energy used = 1/2 of indicated power (more basses is more power, more volume is more power)
For example a 500W sound system uses generally 250W continuously, equivalent to 3 à 4 cyclists.
1 cinéma projection = 4 cyclists
1 coffee = 20 cyclists for heating (or 1h of cycling for your own)
1 pintje = 1h of cycling to burn the calories

The actual system provides place for 4 ordinary bikes to produce the needed power, equivalent to 300W. The peak power comes to 800W. The plugs are standard mains plugs, with the same quality of current as at home.

There is a possibility to set up a low voltage DC circuit, at 12V car cigarate plug or 24V specific plug. This allows the system to be 20% more efficient.

*Salary on pedal energy ?*
_more numbers_
1 day of cycling = 50 W x 8 h = 0,40 kWh
1 kWh = 0,20 €
poverty line = $1.90 a day
cyclists salary = 4% of the poverty line

Sources :



*Traveling trough Brussels with the xyz cargo bike*

Preparation : charge the battery, find the keys, checking the brakes, inflate the tires, take a lock, put the saddle at your height.
Planning the trip : avoid steep hills (Mont des Arts, Botanique, Porte de Namur), the elevator at Palais de Justice fits the bike, calculate your time (then add some for surprises and answering curious passengers.
During the trip : start the bike with the front wheel straight and give some power, when standing up on the pedals watch out for your knees, while in traffic take your place in between the cars, don’t hesitate to give a ring but don’t frighten pedestrians.
At the finish : don’t forget to take care of yourself and drink enough water.


*Battery selection*
_first remark : if you can avoid using a battery and work with the people pedal power in stead, this is considerably more interesting for the environment_
– car batteries a heavy compared with the energy they can store, they are designed for giving high current.
– deep cycle / cyclic / boat batteries can contain more energy because of the internal structure of the battery technology, allowing a deep discharge.
*input* : user power (ex sound system of 900W peak)
*input* : time of autonomy (ex one hour before charging)
*input* : voltage of the system (ex 12V)
*energy need* = user power * time of autonomy (ex = 900Wh for the sound system)

_checking the battery parameters_
– Gel and Absorbent Glass Mat (AGM) types of VRLA can be mounted in any orientation, but need to be ventilated.
– the depth of discharge (DOD) of a battery determines the capacity and the number of cycles, 60% is a good value for AGM batteries (check DOD documentation).
– the current of discharging lowers the voltage output, the higher the discharge current, the lower the voltage and the lower the capacity.
*battery voltage at the DOD* > voltage of the system (ex 6 cel Li-ion doesn’t work, ex when discharging in 3h (0,3C), after 3h the battery voltage drops to 11V)
*charge need* (Ah) = energy need / voltage / depth of discharge (ex = 900Wh / 12V / 60% = 125Ah)

ex DAB12-135EV 12V 166Ah 136Ah 342 173 286 B M8 43,3

The number of cycles of a battery is dependent on the depth of discharge.