Hello all,
First time post here - I was wondering if anyone could help with the following.
I am creating a hydroelectricity workshop for use with school children. The idea is that they design and test blades for a small turbines. These will then be tested under a water flow - probably a water cooler reservoir.
I want to measure the power generated by the motor (dynamo) using an arduino so that the children can get some data from their experiments.
If anyone could point me in the right direction of appropriate online resources or code, I would be very happy.
It might be easiest to simply get a multimeter to measure the voltage and/or current.
You can also hook-up an LED that will get brighter with more voltage.
Do you know how to calculate power (Watts)?
With the Arduino ... You can use an analog input on the Arduino to read DC voltage ([u]Analog Read Voltage Example[/u]). If it's AC, you can use a rectifier to convert AC to DC (although you'll loose a little more than 1/2 Volt across the diode).
If the voltage is above 5V, you can use a [u]Voltage Divider[/u] to knock-down the voltage, and then scale readings appropriately in your sketch.
And, you might want some [u]Protection Diodes[/u] if there is a possibility unknown voltages going into the Arduino and damaging it.
I doubt you'll be working with dangerous voltages, but if it's greater than about 50V, I don't recommend connecting the Arduino directly (even with a voltage divider and protection diodes) because you are getting to where the voltages are dangerous to humans!
To calculate the power output you need to measure both voltage and current at the same time. For DC power, watts = volts * amps.
It is relatively easy to measure and record voltages with an Arduino but it is less easy to measure current in a circuit where the power is doing something useful.
Assuming you don't want to do anything useful with the energy I suggest you use a small incandescent lamp as a load (not an LED). Measure the resistance of the lamp. Wire it up like this
GND ---- generator ----positive--x--lamp----GND
Connect GND to the Arduino GND. Use the Arduino ADC to measure the voltage at x - taking the necessary precautions to protect the Arduino from voltages above 5v.
You will know the voltage across the lamp and the resistance of the lamp so you can calculate the current through the lamp using Ohm's law. And if you know the volts and the amps you can calculate the power (watts).
Hi, until we know the characteristics of the generator we cannot comment on the exact type of load to use.
A lamp is not a suitable load, if you use it cold resistance, the lamp resistance will change with current.
There are a number of ways to measure current, we need to now what sort of range of current and voltage you will be looking at.
If low enough power a simple power resistor will suffice, which would make the power calculation simple.
You output device could be a servo, usings it output arm as a meter needle, and making it robust and LARGE.
Or/as well as a vertical line of LEDs in a bar gragh config and a digital read out.
With arduino this is an ideal project and I will follow to see how you go.
You will know the voltage across the lamp and the resistance of the lamp so you can calculate the current through the lamp using Ohm's law.
If by "enlightenment" you mean also learning about devices that do NOT obey Ohm's law, then an incandescent lamp is one of the classic examples. But this seems to go far beyond a project for schoolchildren.
Measuring the power produced by a generator is not simple, because the power generated depends extremely strongly on the characteristics of the load, as well as the match between the power source and the turbine blades. Ideally you would want to determine the maximum power point for each blade design and for that, you need a variable load and to monitor both the voltage and current as a function of the load resistance. Overall, this would be a project suitable for engineering students.
Hi, yes the light/s idea is good but if you wanted a quantitative measurement you will need a fixed load. Knowing that load you can calculate current and power, so only voltage needs measuring.
You could have an array of lights, representing house holds, and switch them in monitoring the voltage, until the voltage is equal to that rated from the generator, you would then have a visual representation of impeller capacity.
jremington:
If by "enlightenment" you mean also learning about devices that do NOT obey Ohm's law,
Enlightenment was a pun.
I suspect 80% of the kids will just want to see the wheel go round.
A few may be vaguely interested in the fact that electricity is produced.
The teacher can easily say that his measurements are not very accurate.
He could also put an ammeter between the generator and point x to measure the current properly.
In my opinion a whole lot of "proper" scientific equipment will just give the impression that science is hard rather than science is fun. There will be plenty of time to explain the intricacies in future years if you first get the child interested enough to stick with the subject.
The aim of the projects is actually to design turbine blades for a hydro electric power generator.Blades would be attached to a geared motor. Put under a water flow the motor would be driven to produce a voltage. The motor will be maximum 5V - put the power we make will be significantly less that this.
I want the children to visually see the power they are generating. I thought a vertical strip of LEDS that lit up as more power was made - these LEDs powered by a separate power source and used to indicated the amount of power generated.
I'll try out a few of your ideas and then let you know how it goes.
