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.

Sunday, 20 November 2016

Running lights in conjunction with an AC/DC converter,e.g. B&M e-werk

Just investigating what happens when lights are used at the same time as AC/DC converters:


Preliminary considerations:

USB-werk, e-Werk@4.9V, Luxos-U, etc. etc., they all arrive to produce 2.7-2.9W at 20km/h

An e-Werk, the traditional one I mean, will be capable to give you more than above stated powers if set at voltage levels above 4.9V … BUT the immediate above step of 5.6V if intended to be used with a standard 5V-USB load is a bit too much and so far unsafe !!

Another consideration is the following: some AC/DC converters, like the Luxos-U, once loaded with an excessive load, generally say above 500mA, will exhibit a sort of LLV-Low Level Voltage shutdown that for the mentioned Luxos-U is 2.75V approx, in other words below 2.75V it simply powers-off !!

Well, 2.5W are generally more than enough to power a normal gps. Indeed power required by very popular gps devices can span between 0.35W required by a Garmin 60CSx at 0% backlight to a very demanding 2.6W (sometimes even more!!) of a Garmin Montana 600 at 100% back illumination. In other words be careful because power requirements of a gps commonly increases exponentially above 60% back illumination !!!

Let’s come to dynamo: a very standard dynohub marked 6V3W is normally capable to deliver almost 6W at 20km/h whether coupled with its “perfect matching” load. The rating of 6V3W is referred to a resistive load of 12 Ohm, but if you couple it with 30-40 Ohm you’ll easily get almost 6W.

Now let see the matching dynamo-converter issue: when you couple a dynohub to an AC/DC converter like an e-werk, it will be this latter one to determine the usable “transferred power”. That’s why some AC/DC converters will capable to deliver only 2.7W and some other ones will possibly arrive to the double. It’s a pure matter of internal electronics design, a design specifically conceived to optimize dynamo frequencies (20-70 Hz), voltage levels, capacitors charging/discharging, mutual impedance coupling … etc. etc.

NOW, about the story of running lights in conjunction with an USB-werk:

- Well, this is of course the most critical issue to try to give an answer to. To try to give an answer though, I do prefer avoiding extravagant theories and rather totally rely on much more dependable lab tests. To this respect I made the following:

 NOTE:  all my tests have been done using my usual TEST BENCH (i.e. CYCLEEX) alternatively connecting an Halogen or a LED lamp


TEST_1: 20km/h, the B&M Lumotec HALOGEN or LED light are OFF, I adjusted the load to a minimum of 8.7 Ohm to allow the voltage to stay above 4.76V, THE TRANSFERRED POWER TO THE LOAD IN THIS CASE IS THEREFORE 2.6W 

TEST_2: 20km/h, the B&M Lumotec HALOGEN light is ON, I adjusted the load to a minimum of 41.5 Ohm to allow the voltage to stay above 4.76V, THE TRANSFERRED POWER TO THE LOAD IN THIS CASE IS THEREFORE 0.55W 


TEST_3: 20km/h, the B&M Lumotec LED light is ON, I adjusted the load to a minimum of 24 Ohm to allow the voltage to stay above 4.76V, THE TRANSFERRED POWER TO THE LOAD IN THIS CASE IS THEREFORE 0.94W 


CONCLUSIONS: 


- with the headlight OFF you can rely on 2.6-2.7W roughly as expected 

- with the headlight ON you still can rely on some power, depending on the type of light, halogen or LED ! As you can see from the above numbers, in either case you still might have enough power left to supply 0.35W required by a Garmin 60CSx if used at 0% backlight !!

Friday, 23 September 2016

Why not 6 W at 20 km/h ??

So far, after quite an interesting discussion, I came-up to the conclusion that sometimes “EFFICIENCY” might not be at all a top priority. What is most important is indeed the effective power that a certain AC/DC converter can draw from the AC side (generator) of a system and deliver to the DC side (load) at a certain speed. To make it clear once again: “if one device gets an input of 3.0 W at 20 km/h and has an efficiency of 80% and the other device gets a input of 3.5 W at 20 km/h and has an efficiency of 75%, than the second device is the better choice in spite of its lower efficiency”. 
To make evaluations on how good an AC/DC converter is, I personally do not even need very sophisticated laboratory instruments since I make all relevant measurements directly on DC side. To do that I use a real generator, a real AC/DC converter (the one under test) and an adjustable ohmic load made-up of calibrated ceramic resistors. 
Some people make use of very expansive electronic loads, but that's a different story ... 
In my case the wheel/generator speed is controlled and finely tuned via an asynchronous motor powered by a 3-phase inverter. At this point the test method is extremely simple: I adjust (sink) the load till to get the maximum transferred DC power to the load taking care of course that the voltage doesn’t go below a certain “low limit”. For instance for usb 5V voltage I’d set this limit to 4.75V. The results seem to be pretty reliable so far. The basic estimate criteria would be that an AC/DC converter is as better as bigger is the amount of ACTIVE POWER that it will let to flow from the generator to the load. The test system I use is THIS ONE, home made but pretty well performing. Here below a couple of sample plots based on a Shimano DH-3D32-QR hub dynamo and an e-werk respectively set at 4.9V (1st plot) and 5.6V (2nd plot). As you can see the e-werk at 20 km/h doesn’t seem to be able to transfer more that 2.75W. 
The third plot, worked-out by an indipendent lab, http://fahrradzukunft.de/, well confirms above data. 
But what's most important, is that it shows that at 20 km/h some alternative devices, such as Forumslader-V5 or Dynamo Harvester Plus, can definitely do much better arriving to deliver more than 5 W !!



Courtesy of  http://fahrradzukunft.de/

Friday, 25 March 2016

... experimenting "multicolor magnet driven" back lights















Cercavo qualcosa per farmi veramente vedere nei momenti più difficili, nelle gallerie, sotto la pioggia, nell’oscurità della notte. 
Ne è venuto fuori quello che vi faccio vedere nei filmati e nelle foto qui sotto, costruito con materiali di recupero come relay, pezzi di computer, led rgb e “avanzi” vari. 
Un risultato sorprendente, una luce accecante e da attivare esclusivamente nei momenti più difficili e di assoluta necessità. 
Nessuna pila, solo magneti, bobine e led. 
Un qualcosa alla portata di tutti con spesa praticamente uguale a zero !!!



Tuesday, 8 March 2016

Da dinamo a hub USB

DINAMO A 20 KM/H, CONVERTITORE (E-WERK) IMPOSTATO SU 4.9V, HUB USB PRATICAMENTE CONFIGURATO CON TRE LINEE IN PARALLELO 

METTENDO IL TUTTO IN FUNZIONE, LA TENSIONE IN USCITA DALL' HUB USB SI STABILIZZA SU 4.81V; 61 mA VANNO ALLE PILE, 180 mA VANNO AL GPS


ORA STACCO LA DINAMO, LA TENSIONE IN USCITA DALL' HUB USB RIMANE A 4.85V PROVENIENTI DALLE PILE, LA CORRENTE AL GPS RIMANE A 184 mA E PRENDE IL SEGNO MENO PERCHE' ORA PROVIENE DALLE PILE E NON PIU' DALLA DINAMO