Il problema dell'alimentazione elettrica per chi usa la bicicletta, sia nell'uso quotidiano che per viaggi di più giorni, sta diventando sempre più impegnativo. Serve sempre più energia elettrica non solo per illuminare la strada nelle buie ore della notte ma anche per alimentare il sempre crescente numero di dispositivi elettronici a cui non sappiamo più rinunciare. Questo sito vuole essere un primo passo per provare ad orientarsi nella non sempre facile scelta degli strumenti necessari per gestire in modo possibilmente autonomo le proprie necessità.

The electric power supply problem for people who like to cycle either in everyday use and along trips of several days, it's becoming increasingly challenging. More and more electricity is indeed required not only to illuminate the road in the dark hours of the night but also to feed the ever growing number of electronic devices that we can't live without. This site aims to be just a first step in the attempt to orientate the user in the not always easy commitment to choose the most appropriate tools.

Friday, 26 October 2018

Dynamo Voltage Hazard

When I was young I remember that I often used to adjust with the right hand the sidewall dynamo connection-wire sometimes accidentally coming loose while cycling. Making sure to secure at the same time with the left hand the handlebar on a not very well insulated grip I remember also that some perceptible and quite annoying leakage current was indeed crossing my body.


Well, IEC-International Electrotechnical Commission states that for voltages around 50V human body on a hand-to-hand pattern has an impedance of about 1500 Ohm or even less, that one significantly depending on actual body mass, skin conditions, contact area, applied voltage, frequency, etc. 
Now the point: at 50 km/h at no-load conditions, or on a 1500 Ohm load with no significant difference at all, out of a dynamo without a built-in voltage protection you may have something like 50V that applied to your body might induce in turn something like 30 mA. Something definitely unlikely to happen, I agree, but still possible … especially for grounded hub dynamos and spoilt head lamps with exposed/not well protected live parts. 
From the point of view of a possible exposure hazard IEC worked out the below Current-vs-Time plot identifying four zones: 

Zone 1: represents the limit for current perception estimated to be 0.5 mA 

Zone 2: represents the danger threshold generally recognized still to have no dangerous physiological effects 

Zone 3: it’s a sort of an “alert” area coming just before any possible atrial fibrillation, mainly characterized by yet reversible physiological effects such as muscular contraction (tetanization), difficult respiration and cardiac disturbances. As you can see 30 mA for one sec may already have some annoying effect. 

Zone 4:is characterized by permanent effects, such as fibrillation, depending, beyond current and time, also on specific health conditions. Contact times as low as 10 ms may be lethal but fortunately these current values seem to be much higher than those ones actually supplied by a dynamo at 50 km/h !!




Wednesday, 24 October 2018

PowerPack Actual Capacity

POWERPACK 
In commercio esistono ormai powerpack per tutti i gusti e tutte le tasche. Ma vi siete mai chiesti un determinato powerpack quanti mAh concretamente potrà mai trasferire al dispositivo da caricare, ovvero quante volte lo potrà ricaricare ? Tempo fa avevo fatto una stima in base alla quale durante il “travaso” sembrava che se ne dovesse andar via il 30% circa. In effetti sembrava allora una previsione pessimistica; mi sono allora deciso a fare delle misure concrete (e piuttosto accurate) e ho visto che nel “trasferimento” si perde per strada la metà circa dei mAh di partenza … altrochè il 30% !!! Tradotto in pratica con un caricatore da 20000 mAh non potrete caricare più di cinque volte una batteria da 2000 mAh come qualcuno potrebbe pensare !!! Per fare le prove ho collegato l’uscita USB-5V del mio PowerPack da 21.000mAh equivalente a 77,7 Wh su una resistenza da 10 Ohm e per tre volte consecutive ho notato che il processo si è fermato a meno di 40 Wh … cioè circa la metà dell’energia di partenza !!! Ora, per la cronaca, vorrei ricordare che per fare 40 Wh con una dinamo al mozzo basta pedalare 13 ore !!

 

Thursday, 17 May 2018

Lighting-up from 3.9W to 5.4W using a common 6V-3W dynohub

Based on some tests performed on a common 6V-3W dynohub (Shimano DH-3D32) span at an equivalent of 20 km/h on a 28” wheel and connected to a variable resistive load, I plotted Power vs Load Resistance getting a maximum of power at about 30 Ohm load.
At this point I tried several filament lamp configurations aimed to get closer as much as possible to the above indicated optimal resistance.
In the WIRING DIAGRAM below all labelled powers and relevant resistances are the nominal ones whereas in the next table all reported numbers are actually measured values.
CONCLUSION: using a 3-ways single pole selector (S1) it seems to be possible to have the following lighting modes:
S-0 - OFF
S-1 - Common Head and Rear Light combination mode (normal mode)
S-2 - Reinforced double front light configuration mode (flood mode)

REMARK: as said above all tests have been performed with very common tungsten filament, it’d be interesting to repeat same test either with alogen filament lamps and led lights.





Thursday, 10 May 2018

USB Chargers

ALL CHARTS AND INFORMATION BELOW BASED ON 
Fahrradzukunft [https://fahrradzukunft.de/]
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LEGEND
- Ladesleistung in die Akku-zellen = battery charging power [W] 
- Fahrgeschwindigkeit = speed [km/h], all data based on SON28 assembled on a 28” wheel
HIGHLIGHTS&CONCLUSIONS: with some models at 20 km/h it seems to be possible to have up to 5.5W transferred power to the internal buffer battery



LEGEND
- Max Dauerhafte USB-Leistung = max permanent power at USB output [W]
- Fahrgeschwindigkeit = speed [km/h], all data based on SON28 assembled on a 28” wheel
HIGHLIGHTS&CONCLUSIONS: with some models at 20 km/h it seems to be possible to have up to 5.0W permanent power at USB output




LEGEND
- Wirkungsgrad Akku zu USB = efficiency power_battery/power_USB [%]
- Entnahmeleistung am - USB-Anschluss = power on USB output [W]
HIGHLIGHTS&CONCLUSIONS: with some models at 3W USB output it seems to be possible to reach up to 84% efficiency ( ??? )


LEGEND
- Fahrgeschwindigkeit = speed [km/h], all data based on SON28 assembled on a 28” wheel
- Electrische Leistung Dynamo = dynamo electrical power [W]
HIGHLIGHTS&CONCLUSIONS: with some models at 20 km/h it seems to be possible to have up to 6.5W transferred power from the dynamo to the charger