[The students] would like to hook up a [bicycle] dynamo to a hometrainer to do 3 things:
1) Charge a phone
2) Power a small fan (12V)
3) Charge a battery pack
A bicycle dynamo (alternator) does not have a voltage regulator. When the dynamo is spinning fast then its voltage is much too high. A car alternator has a voltage regulator that prevents its output voltage from exceeding 14.5V but the alternator can still produce almost its rated voltage when spinning fairly slowly (a bicycle dynamo cannot).
The zener diode in the circuit shown turns on the Mosfet when the voltage becomes too high and the Mosfet and its resistor overloads the dynamo to prevent high voltage. I suspect that the light on a bicycle overloads the dynamo to prevent its voltage from going too high. You must find a fan that uses the same current as a bicycle light, but if the light and fan are both turned on the dynamo will be overloaded and its voltage might be too low.
The circuit shown and a voltage regulator IC will do nothing to boost the voltage when it is too low. A circuit called a "boost/buck converter" is what is needed to boost or buck the voltage from the dynamo. More complications.
Good move; that is the way to succeed- divide and conquer.Ok so i'll start out slow and look for all the needed equipment.
No probs and a good approach. 5V fans are freely available.We'll go for a 5V fan so we can use 1 circuit thanks for the advice.
The peak inverse voltage (PIV) of the diodes will affect nothing, providing that the PIV is higher by say 20% than the voltage that the diode will be subject to in the circuit. The two other important characteristics are the diode speed (unlike your mains supply which has a fixed frequency of 50Hz, a dynamo frequency will go much lower and higher) and the voltage drop when current is passing through the diode in the forward direction. Schottky diodes are particularly good in both of these respects. The diodes that I have specified are widely used and are dirt cheap, so I would advise going for those.If I get another rectifier with for example 150V will it influence the circuit in a negative way?
ExcellentAnd we'll try a light first and then we'll move on.
Yes, a step-up/step-down (a type of converter that does both) DC to DC converter will be best, but you could probably get away with a step down converter. This will all be thrashed out in the detailed design phase.Do i need a power regulator 5V at the end of the circuit.
The bridge rectifier and reservoir capacitor in the circuit of post #5 convert the AC from the dynamo (alternator) into DC. By the way, 6V RMS rectified will give 1.414 (root 2) * 6V = 8.5V. You need to subtract the two forward voltage drops caused by the diodes = 2* 0.4V = 0.8V to give a final DC voltage across the reservoir capacitor of 7.7V.Why do i need the Zener diode
1) I've started with Arduino projects but do you guys know good books, tutorials, courses, etc so that i can make my own "simple" projects? I've been following the manual untill now.
2) What equipment is essential when starting with [the Arduino] project?
The article just lists core components that I recommend for starting out in electronics. For your project you will not need all the components unless you plan on setting up a general electronics facility at your school. I have also, just posted a draft article, describing 'core electronic equipment' to get started in electronics @ https://www.electro-tech-online.com/articles/core-equipment.787/I'm going to start out by reading the article and getting the basic supplies that I don't have yet.
Yes, it will be fine to test the principle with a low-power bicycle dynamo. The normal power is 3W, rather than 6W.After that I'll have a go later this week at finding a stronger power source.
The price will be higher I guess but can I test out the circuit with a low power bike dynamo without connecting a device?
I can just measure the current and voltage to see if I didn't make a mistake. What should the output voltage be? around 5V?
Apart from bicycle dynamos, dynamos are rare and expensive. But having said that, there is absolutely no reason why you could not use a permanent magnet motor as a generator. A 50W or greater 12V fan motor would be a good choice. Fans are available either free, from scrap equipment, or at low cost, new.Does anyone know a better power source? I found some 12V dynamo's but they're pretty expensive for an experiment.
No probs. The Pi is well worth investigating. You may read that the Beagle Bone single board computer is better than the Pi, and so it is, technically. But the Pi will be more than adequate for your and your students needs and is much better supported. In the meantime, here is a link to the Pi Organization home page. You can download the free Pi magazine and tutorials. https://www.raspberrypi.org/Thanks for the information. I'll also be looking into the raspberry Pi this weekend.
The electronic components will be identical and, in general yes, the shields will be compatible, but you will need to make different connections to the Pi input/output pins. I am not sure what a sim900 shield isThe shields and equipment (sensors, capacitors...) will work for both I presume? Because I've ordered a sim900 shield last week.
Hey Camerart thank you for the advice. The drawing that spec made is indeed really clear and can help me explain how the AC turns into DC.
But just to be sure is the only function of a diode to let the current pass trough in one way and block it from going the other way?
JonSea: do you have experience with these water turbines? Do you know the output voltage and current?
spec: I'll also be on the lookout for old fans so I can let my students test the different options (for voltage and current) and let them decide what they think will be the best option.
greetings Sander
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