Bike Generator

No matter how good anybody designs or builds a bike generator, it is never going to save you a lot of money. Do you want to know why not? You can read that in step 1 here below where I calculate what you can save with a bike generator and how you can save more money in another way with the same effort.

Why did I then start this project? Well, I wanted to learn more about the way electric motors and generators work, which voltages I would get out of my generator and what I could do with that energy. The end result is that I built a bike generator from an old bike, a broken washing machine motor and some left over metal from previous projects, while spending only 2 euros on the entire project (to buy a new bearing).

As you can see on the photo I could power a light bulb and a hand mixer and charge the battery of a torch all at the same time by just pedaling on my bike generator. Does that mean that I generate a lot of power? No. It just does not take much energy to charge a battery, the light bulb was not that bright and the mixer was moving at low speed and only mixing some air.

I have seen other Instructables and YouTube movies about bike generators, but most people use a DC motor or car alternator and often they use a battery and an inverter and I did none of that, so I will share with you what I did.

I will cover a lot of details and test results. Here below you can see an overview of what I will describe, so you can skip all the details that you are not interested in and scroll down to the steps with the information that you would like to know.

Step 1 gives a calculation of the maximum amounts of energy and money that can be saved by using a bike generator.

Steps 2-8 show what I did on the mechanical part of the motor. Taking it apart and replacing the bearing. It also shows what a universal motor looks like internally.

Steps 9-14 describe what I did on the electrical parts of the motor including the first tests as a generator.

Steps 15-26 explain what I did to custom build a bike stand and attache the generator to it. If you are only interested in building a DIY bike trainer from scrap, these steps might still be useful. If you cannot weld, you can build something similar from wood or buy a bike trainer.

Steps 27-30 show my tests and actual results for the bike generator.

SAFETY REMARK: In this project I got voltages up to 160 VDC. That can hurt you, so be careful.

I already mentioned that I did not want to spend any money on this project and that is because I started by calculating what the energy production and cost savings would be even in the most ideal situation.

First we need to know how much power a human can generate by pedaling a bike. I searched online and found that a beginner will probably produce an output of 100 Watts. A healthy person with good stamina will produce about 200 Watts and a professional cyclist will produce 400 Watts. That is the average output they can produce during a workout of an hour. Of course it is possible to reach higher values during a short sprint of a few minutes, but that is not what I am looking for, as that is not very useful for continuous power generation.

I based the calculation on the quite optimistic idea that I would be able to produce 200 Watts continually during a workout of an hour, although in reality I will probably lack stamina to be really able to do that.

Producing 200 Watts on the pedals of the bike does not yet mean that a generator will also produce 200 Watts of electricity. There are always losses involved in converting mechanical power into electrical power and those losses can easily be more than 50% of the input power. All the friction in the bearing of the pedals, in the bottom bracket, in the chain, in the derailleur and in the rear hub of the bike are losses. Also any slipping between the rear wheel and the generator shaft is a loss. And in the generator there are losses by friction in the bearings, by resistance in the copper wires and connectors and losses in the iron by the magnetic fields. I did not use components like a voltage regulator, a battery or an inverter, but some other people do use them and all those components also have efficiency losses.

There will be differences in efficiency depending on the chosen design and on the quality of the used components, but it will never be possible to get an efficiency of 100% as there will always be losses. Still I am going to base my calculation of the produced energy on theoretical best case scenario that there are no losses. You will see that even if there were no losses at all, the amount of money that can be saved by producing your own energy is really low.

And again being too optimistic, I assumed that I would work out on the bike generator two hours per week during the entire year, which is 2 hours/week during 50 weeks per year, so 100 hours per year.

In the most optimistic scenario I will produce 200 Watts during 100 hours per year, which is 200 x 100 = 20,000 Watt hours per year. Electricity is usually calculated in kilo Watt hours (kWh) and since there are 1000 Watts in 1 kilo Watt, I have to divide 20,000 Watt hours by a factor 1,000 so 20,000/1,000 = 20 kWh per year.

Let's compare that to the yearly electricity consumption of an average family. If you live alone and do not use a lot of electricity, you will probably still use at least 1,000 kWh per year. And if you have a family with some children and you have an air conditioning and washing machine, microwave and several other machines, you will probably use between 3,000 and 4,000 kWh per year.

So let's assume that you are the person that only uses 1,000 kWh per year, then 100 hours of exercising on the bike generator without any efficiency losses, will still only produce 20 kWh out of a total of 1,000 kWh, which is just 2% of the yearly electricity consumption. And if your yearly energy consumption is 4,000 kWh per year, the 20 kWh from the bike generator is just 0.5% of the yearly energy consumption. And that is an optimistic estimate as in reality the bike generator will produce less due to efficiency losses.

Let's also look at how much money we can save by producing 20 kWh of electricity per year. Prices of electricity can vary but at the moment we pay about 0.30 euros per kWh. This means we can save 20 x 0.30 = 6 euros per year on our electricity bill. (This is less than 7 US dollars per year.) And remember that all my assumptions were very optimistic, so the real savings will be lower than that. Therefore, no matter how good anybody designs or builds a bike generator, no matter which type of motor or alternator they use and no matter how fit they are, the total savings are always going to be really, really low.

This is the reason that I do not want to spend any money on my project. I just want to learn and experiment with a bike generator and after that I will use it as a bike trainer just to be able to do a workout without having to go out in cold and wet winter conditions.

By the way, there is another way to save money by riding a bike. If I would use my bike 100 hours per year to go somewhere instead of driving my car, that would result in much higher savings.

Let's calculate how much money I would save on fuel for my car if I used my bike:

Suppose I will cycle at an average speed of 20 km/h (12 mph).

In the same 2 hours per week, so 100 hours per year I would ride 20 x 100 = 2,000 km (1,250 miles)

My car uses about 1 liter of fuel for every 15 km, so that would save me 2,000 / 15 = 133 liters of fuel per year (35 gallons).

One liter of fuel costs approximately 1.50 euros here in The Netherlands, so riding my bike instead of driving my car will save me 133 x 1.50 = 200 euros per year. (USD 230 per year.) In other countries the fuel prices might be lower, but even if fuel costs are only half of what we pay here, the savings of riding a bike instead of a car are still much higher than the savings made by a bike generator.

Conclusion:

Do not build a bike generator if you want to save money. Also do not build a bike generator if you expect to be able to power your house with it. You will at best only produce about 2% of your yearly consumption. But if you want to learn and experiment and enjoy the possibility of getting some exercise in your own house, this can be a fun project.

I got the washing machine motor from a washing machine that was broken. However, that does not automatically mean that the motor itself has to be broken, therefore I first had to check it.

I tried to rotate the pulley which is indicated by the red arrow and it did not move at all. A good motor should spin easily and even keep spinning for several seconds when you give it a spin with your fingers. Obviously my washing machine motor had a problem.

My washing machine motor had 4 long bolts that keep everything together. They are indicated by the green arrow.

Tip 1: I advise to measure the distance indicated by the red arrow at each of the 4 sides, before taking the motor apart. When you reassemble the motor, you will then know exactly how far the bolts have to be tightened and by checking that the distance it correct at all four sides, you prevent problems with alignment. (Of course I did not do this the first time, so I had to learn the hard way.)

Tip 2: I struggled to loosen the 4 bolts and even ended up cutting the original ones with a hacksaw. When I reassembled the motor I did not have the right length of bolts, so I used threaded rods instead of the original bolts. The reason that I struggled with loosening the bolts was that there is a spring inside which is putting tension on the bolts. It helps to use some clamps on the points indicated by the blue arrows to slightly press both ends of the motor inwards and then it is real easy to loosen or tighten the bolts and you can use the original ones.

Tip 3: Make sure you can remember how all the parts are connected. If needed use a marker to mark where each side of each component touches the next component.

On the second photo you see the main components of the motor. The rotor is the rotating part of the motor, while the armature remains stationary. This motor is a series wound universal motor and can run on AC and DC. In Europe this type of motor is used a lot in washing machines but there are also other types of washing machines with different motors. If you have a washing machine motor that looks completely different from mine, it might operate differently.

The bearing of the rotor was stuck and you can see at the location of the yellow arrow that the side of the bearing came off and is damaged. I removed the old bearing, spent 2 euros to buy a new one and used a socket and hammer to hammer the new bearing in place.

Tip: I advise to measure the location where the old bearing was before replacing it. I again learned this the hard way, because I had not hammered the bearing down fully and after reassembling the motor it still did not spin smoothly.

Since my new bearing was not exactly in the right spot, the carbon brushes were no longer touching the collector in the same place as they had always done. You can see that there is a gap indicated by the green arrow where the carbon brushes are supposed to touch the collector.

A relatively new collector should not have worn so much, but I am using an old motor and there was really a lot of additional friction in the motor when the carbon brushes where not in the groove.

So I took the motor apart again and hammered the bearing down a bit more so the carbon brushes could end up where they had always been.

Many people that built a bike generator use some kind of belt on the rim of the bike's wheel and on the pulley of the motor. I did not want to do that because I did not have such a long belt and I expect that a belt will slip a lot because the bike's rim does not have the right shape to act as a large pulley. So instead I decided to drive my motor directly by the tire and therefore I needed something with a rough surface on the location of the motor's pulley so the tire would not slip over the pulley.

I clamped the rotor in the vise and used a puller to remove the pulley. As a replacement I used a part that came from the broken washing machine and drilled a hole in the center on the drill press. Of course the inner diameter of the hole should match the outer diameter of the axis of the rotor at the point where the pulley used to be.

After drilling the hole I used an angle grinder to cut off the section that I needed. I inserted it on the rotor and since it was slightly loose, I added 4 small tack welds to keep the replacement for the pulley firmly attached to the rotor. In hind sight it would have been better to keep more distance between the motor housing and the new "pulley" to prevent that the tire of the bike will rub against the housing of the motor.

Actually I have assembled and reassembles the motor several times because I did not yet know about the tips that I shared in the previous steps.

Summarized:

• Use a marker to indicate how each component is connected to the next one.
• Make sure that the new bearing is in exactly the same place as the other one.
• Use threaded rods if the original bolts are broken.
• Make sure the spring (shown on the third photo at the bottom right side of the photo) is in the right place and the bolts are tightened enough to get the right tension by the spring. To check this make sure the distance between both sides of the housing are equal to what they were before disassembling the motor.
• Make sure there is enough space for the tire of the bike to drive the "pulley" without rubbing against the housing of the motor.

Here in this step you see the electrical wires still connected to a connector while on the photos of the previous steps this connector was not always present. That is because I worked on the electrical parts already during disassembly of the motor, but for the description in this Instructable I think it makes more sense to separate the mechanical steps and the electrical steps.

So on the first photo you see all wires connected to a white plastic connector. I used a screw driver at one side while pulling on the wire at the other side and the wires came out one after the other.

Then I had to find out which wire is connected to which component. (Please be aware that the colors of the wires may be different for different brands of motors, so the colors on itself do not really give you any information.)

The black cap which is shown on the third and fourth photo is the housing of a speed sensor. I do not need that sensor, so I removed the two yellow wires connected to that sensor.

That left me with 5 remaining wires: white, blue, black, brown and yellow.

First check which color of wiring is connected to both carbon brushes. In my motor that is the white and the blue wire, so those wires a connected to the rotor via the carbon brushes.

Then I had three wires remaining: brown, black and yellow and all three were connected to the armature.

I measured the resistance between each pair of wires and got the following results:

• brown-black gave 1.2 Ohms
• black-yellow gave 0.6 Ohms
• brown-yellow gave 0.6 Ohms

This means that the yellow wire is connected to the center between of both armature windings and I do not need that connection. So brown and black are my armature connections.

I also measure the resistance between the blue and yellow rotor connection and got 5.4 Ohms there.

If the resistance that you measure is completely different from my results, your motor might have an electrical problem or your wires are connected to something else.

A universal motor will run on AC and on DC, but if you use AC on a universal motor that is not connected to any load, the motor will ramp up quickly to a far to high speed and usually it will destroy itself. In the washing machine itself there is a control circuit to prevent that, but I do not have such a control circuit, so I will only test the motor on DC.

For that I used my home made power supply that I once made from an old computer power supply. I have the possibility to connect the motor to + 3.3 VDC, + 5 VDC and + 12 VDC. I tried all three voltages but the motor only runs on +12 VDC.

Then I tried all possible combinations and marked the housing of the motor with a black and red arrow to keep track of the direction the motor is turning. Of course the black arrow is the other direction than the red arrow.

(Remember that blue and white are connected to my rotor and brown and black to my armature)

+12 VDC - blue (rotor) white - black (armature) brown - ground --> motor turns in the direction of the black arrow.

+12 VDC - brown (armature) black - white (rotor) blue - ground --> motor turns in the direction of the black arrow.

+12 VDC -blue (rotor) white - brown (armature) black - ground --> motor turns in the direction of the red arrow.

+12 VDC - black (armature) brown - white (rotor) blue - ground --> motor turns in the direction of the red arrow.

So to change the direction of rotation I have to connect white to black for the direction of the black arrow and white to brown for the direction of the red arrow.

Anyway the motor was running quite OK in all four combinations that I tested.

I wound a rope around the pulley and pulled on the rope so the motor was spinning just a few seconds. I had a Volt meter connected to the black and blue wire and the white wire was connected to the brown wire and I pulled he rope in the direction of the red arrow.

The result was a short voltage of 0.77 Volts. Not really a lot but at least is was a start.

(You might notice that I did this test when the original pulley was still present on the motor. I changed it later because that pulley did not work well with the tire of the bike.)

I had an old bike that I had not used in the past 8 years or so and of course it was really dirty, so I first cleaned the bike a bit.

Then I placed the bike upside down so the rear wheel was exposed and placed the motor on a stool behind the bike for a second test. It involved two persons as one of us was pushing the motor against the tire while the other rotated the bike pedals manually.

At first this did not work well at all, because the original pulley was too smooth and the tire just slipped without really spinning the motor. So that is when I changed the pulley as already described in steps 6 and 7.

I used the two yellow wires which I removed from the speed sensor in step 9 and soldered them to a 12 V light bulb for a car. I connected this light bulb to the generator while spinning the pedals manually as best as I could but there was no light. Then I measured the resistance of the light bulb including wires and the first result was 864 Ohms (0.864 kilo Ohms) and the second result was 51 Ohms. I measured it a few times more and got different results all the time. Then I decided to cut the aluminum ends of all wires and to use the copper of the wires for the connection. That helped a lot and I managed to produce 80 Volts on the volt meter during one of the tests. (With one of us manually pedaling the bike and the other person busy with pushing the motor against the tire, there was nobody left to take a photo of this.)

Now it is time to build some kind of support for the bike so I can actually pedal using my legs instead of my hands.

I wanted to use the rear tire of the bike to directly drive the generator shaft. So the rear wheel needed clearance from the floor while being supported by some bike stand. Of course the bike stand should not interfere with my feet while pedaling.

A commercially available bike trainer could be used, but I did not want to spend money on this project, so I decided to build something out of available materials. A few months ago I built a fence using rebar and I had a few remaining pieces so I decided to use that. (You can check my previous Instructables for the fence if you are interested.)

I placed a slipper on the pedals, supported it by a white bottle and then used some pieces of threaded rod to get an idea about the required length of the rebar. I liked this setup so I measured the length of each piece and the angle between them.

I needed:

1 piece of 75 cm

1 piece of 45 cm

2 pieces of 42 cm

2 pieces of 39 cm

The angle between both pieces that go to the axis of the bike was 60 degrees.

(I like welding and therefore I tend to make things out of metal. Of course you can avoid this by either using a commercially available bike trainer or by making something from wood.)

I measured and marked the right length for the pieces of rebar and cut them with an angle grinder and compared them with the general idea. Then I marked an angle of 60 degrees on my welding table and welded the first two pieces together.

Sometimes it can be challenging to keep all parts in the right place for welding. I used clamps and magnets to keep both horizontal pieces of rebar at exactly the right distance of eachother. I measured that distance from my test set-up and it was 37 cm. The two vertical sections already had the 60 degree angle so all I had to do is to make sure they were at the right distance from the center and both sides were symmetrical.

On the long horizontal part (of 75 cm long) both connections are 66 cm apart.

On the short horizontal part (of 45 cm long) both connections are 36 cm apart.

On the point where the axis of the bike will be (simulated by the pipe) the distance is 20 cm.

After setting this structure up and holding it in place, welding was easy.

I did a little strength test and checked if the bike stand would fit the bike and it did.

The rear axis of my bike is the type which you can quickly remove. So I removed it and took it completely apart. I wanted to make an extension to the axis that fits both sides indicated by the blue arrows. I had some short pieces of tubing available and two bolts and nuts to make it.

I checked all the scrap pieces of tube that I had and used a hacksaw to cut a short piece of the pipe where the inner diameter was the best match for the first side of my bike's axis. Then I used an angle grinder to cut two slots in the short piece of tube so it would fit over the "wings" of the piece of the axis.

Of course it was not a perfect fit immediately, so I fine-tuned the slots a bit with a small file and used the bench vise to squeeze the piece a bit and then it was quite a snug fit.

For the second side of the bike's axis I cut two pieces of tubing of a different diameter so the smallest one fitted inside the larger one. I drilled a hole through both pieces of tube, placed both of them over the piece of my bike's axis and used a bolt to join the pieces together.

Here again it was not a perfect fit, but during final assembly I used a little piece of tape to wrap around my axis before sliding the pieces of tube over it. That filled the gap and made it a snug fit.

This fire was not intentional, but it was also not really surprising that it happened. I wanted to weld a bolt to both connectors which I made in the previous two steps. After the first tack weld I saw some weld spatter on the threads, so I wrapped the threads in tape before continuing the welding. The heat from welding then set the paper tape on fire, but the threads came out without any additional spatter so it did work.

I used a small file to remove the tiny bits of spatter from my first tack weld and then I had two connectors that fit on the axis of my bike.

I connected the pieces that I made in the previous step to the bike's axis and measured and cut a piece of steel that would fit between the bolt and the bike stand. Then I connected that piece to the axis to keep it in place for welding.

To be able to use my hands for welding, I used a clamp to hold the piece in place and welded it. Then I decided that having a slot in the bike stand is better than using holes, so I used a grinder to turn the hole into a slot. Then I places the rear axis of the bike in the bike stand and tightened the bolts. It feels quite solid.

I also added two additional pieces of rebar to connect the front of the bike stand to the rear. Before I added those pieces there was a little bit of flexibility in the bike stand that I did not want and these additional pieces solved that.

Remark: I have never actually seen or touched a commercial bike trainer but I read that the rear wheel can slightly tilt in those bike trainers. I did not want to have this tilting of the rear wheel because my rear wheel needs to make a good contact with the axis of the generator without rubbing against the housing of the generator.

I used a scrap piece of square tubing and placed it under the generator and that looked like a good solution to support the generator.

I cut an old piece of inner tube to get rubber between the generator and the bike stand. It is intended both as some electrical insulation and as mechanical friction to prevent that the generator slides away from the tire.

I also cut a piece of steel strip, drilled holes for threaded rod and welded the square tube to the bike stand.

With the square tube firmly connected to the bike stand, I placed the generator in the right position and added the steel strip and tightened the nuts.

Tip: It helps a lot to deflate the tire before placing the generator so the tire does not push the generator out of place when tightening the nuts. When the generator is in place the tire can be inflated again.

I had never used Tinkercad before but I have seen people using it in Instructables so I decided to try 3D-printing some legs for my bike stand.

I was surprised how easy it is to make a simple shape like this in Tinkercad, so I had them printed and used the feet to prevent that the rebar will scratch the floor.

Originally I thought about making the feet from wood, but these red 3D-printed feet look much better.

Now it is time to start testing!

I grabbed a volt meter and several other test objects, like a 12V and 24V computer fan, a 6V light bulb from a bike, a 12V light bulb from a car and a 230V light bulb.

Next question is: how to connect each wire? For that is it important to know the difference between a self-excited generator and an externally excited generator.

My washing machine motor is an universal motor and does not have any permanent magnets. However, a generator can only produce electricity if the electric windings pass through a magnetic field. This magnetic field can be produced by an electromagnet, but an electromagnet needs electricity. Only that electricity is not yet there if the generator is not running....

In an externally excited generator, a small electric current from an external source is fed to the field windings in the armature. This current turns the armature into an electromagnet and when the rotor spins through this magnetic field, it generates electricity. In step 29 I will describe my results with the generator as externally excited generator.

The other alternative is to use the generator as a self-excited generator. That means that no external power source is used, but it does not always work. Only if there is a little bit of magnetism remaining in the iron parts of the generator, it can be used as self-excited generator. The remaining magnetism should just be enough to generate a little bit of electricity when the rotor is rotating. Then this produced electricity is first fed to the field windings in the armature to increase the magnetic field, so the rotor can produce more electricity. I will now first describe my results with the self excited generator in step 28.

Actually I struggled a lot to get the generator working as self-excited generator.

Series: white wire connected to the black wire.

In step 11 I tested the motor as DC motor. To get it moving in the direction of the black arrow, the white wire of my rotor had to be connected to the black wire of the armature. (Remember that blue and white are connected to my rotor and brown and black to my armature)

• My bike wheel would spin the generator in the direction of the black arrow, so I connected the white wire to the black wire and connected a 230 V, 40 W light bulb to the blue and brown wire and started pedaling. No light.
• Then I connected a 12 V, 21 W light bulb instead. Again no light.
• I pedaled harder. Still nothing.
• Then I assumed the remaining magnetism might be insufficient and I added some permanent magnets at the outside of the armature. Again without result.
• Then I added a voltmeter. With just a voltmeter connected to the blue and brown wire, I measured 5.5 volts.
• I added a 12 V, 2 Watts computer fan parallel with the volt meter. The fan was not moving, but the volts reduced to 3.1 volts.
• Then I used a 6 V light bulb from a bike. No light and only 0.5 volts on the volt meter.
• Then I connected the blue wire to the brown wire and connected my loads to the white and black wire. The results were similar and still no light and no moving fan.

So all combinations that I could think of with the wires connected in series in the direction of the black arrow did not work...

Parallel

I knew that generators can be series wound, shunt wound or compound wound.

Series wound means the rotor and armature are connected in series and there are a few windings in the armature made of thick wire.

Shunt wound means the rotor and armature are connected in parallel and there are many windings in the armature made of thin wire.

Compound wound is a combination of series and shunt wound windings.

I only have thick wires in the armature, so based on the construction, I could only make a series wound generator if I used the self-excited principle. Still I decided to see what happened if I connected the armature parallel with the rotor. As expected it did not work.

Series: white connected to brown

Finally I decided to connect the generator again with the rotor in series with the armature, but now I connected the white wire to the brown wire. In my tests with the motor used as motor, this resulted in the motor rotating in the opposite direction. But here used as generator it finally worked! I do not fully understand why, but I assume it has something to do with the direction of the magnetic field used as generator and as motor.

• I connected a volt meter and 6 V bike light to the black and blue wire. I got a short flash of light and then the bulb was broken, but the volt meter kept showing 5 volts.
• Then I connected a 12 V computer fan. It works! And I measure 8 V on the volt meter.
• With a 24 V computer fan, it also works and I produce 10 volts.
• A 230 V light bulb does not work.
• A 12 V, 21 W light bulb works, but not great. The light goes on but immediately it gets to heavy to keep pedaling, so I cannot get the wheel to rotate and the light goes off. Then there is no more current through the field windings, so the magnetic field disappears and it becomes easy again to start pedaling. But then the current starts flowing again, the magnetic field gets stronger and the resistance on the pedals increases again and I cannot keep pedaling.

Conclusion:

Using a series wound universal motor as self-excited generator is possible, but only with a light load that uses a small current like the computer fans do.

Fortunately my results for the externally excited generator are much better.

I used my power supply that I built in the past from a computer power supply. The three black holes at the bottom are all connected to ground, so it only matters if the red wire is plugged in the 12 V, the 5 V or the 3.3 V power supply.

I connected the 12 V, 21 W light bulb in series with the field windings to increase the resistance and limit the current through the field windings.

When I use the 12 V supply, I had 2.0 Volts and 1.5 Amps over the field winding, so that is 3 Watts for the external exciting of the field windings.

When I use the 5 V supply, I had 1.3 V and 0.9 Amps over the field winding, so approximately 1 Watt for the external exciting of the field windings.

I also did some testing with an actual controllable power supply.

1 Amp over the field winding makes it easy to pedal, 2 Amps over the field windings is a bit harder but still not difficult. When I use 3 Amps over the field windings it gets harder to pedal and at 4 Amps it is getting quite difficult to keep pedaling.

I like it best to have approximately 1.5 Amps over the field windings, so I kept using the 12 V power supply with the 21 W light bulb in series with the field windings. So I connected the red + 12 VDC wire to the yellow wire of the 21 W light bulb. The second yellow wire from the 21 W light bulb is connected to the black wire of the armature. The brown wire of the armature is connected to the black 0 V wire of the power supply. The white and blue wire from the rotor are connected to a 230 V, 40 W light bulb with the volt meter parallel.

I kept the same setup as in the previous step, so externally excited with 3 Watts, but now I connected power sockets to the white and blue wire of the rotor. The volt meter is connected to the white and blue wire on the connectors of the carbon brushes.

As you can see on the volt meter, I produce approximately 160 Volts DC in this way. The voltage depends a bit on how fast I pedal, but in general it is between 120 VDC and 160 VDC.

SAFETY REMARK: 160 VDC can hurt you, so if you are going to build this generator, make sure that you cannot touch any connections where this voltage is present.

You can also see that I can power a hand mixer and a light bulb and charge a battery at the same time.

I tried connecting the hand mixer because it is a universal motor and I could power it quite well. It is a 350 W machine and designed for alternating current, but since it is a universal motor it also runs on direct current. Many machines have universal motors, for example a blender, a jig saw and a drill and many other machines all have a universal motor. And although it is quite easy to get a universal motor to run on limited power, it does not yet mean that I can also actually use it. As mentioned in step 1 I cannot produce the full 350 Watts for the mixer. So it moves but not with much power and it will struggle to really mix anything. And if I power a jigsaw, it will move, but if I try to cut any wood, the saw will not really be able to cut the wood.

The 230 V, 40 W light bulb also does not mind if it gets alternating current or direct current. It will just glow when a current flows through the light bulb. When powered by the bike generator it produces some light, but not as bright as when I plug it in a wall socket.

Then I tried to charge the battery of the torch. I chose a torch because I did not want to try charging the battery of my phone. I think that will work, but do not want to risk damaging my phone. I read online how phone chargers work and they start with a bridge rectifier that changes alternating current in direct current, so I figured that a charger should also work on direct current. And indeed it does because charging the battery of the torch is no problem.

So my generator works much better as a externally excited generator than as a self excited generator.

But back to step 1: how much energy can I really produce?

I produced approximately 40 Watts as peak output, which is only 40/200 = 20% of the theoretical amount that I calculated in step 1. So if I would be pedaling on this bike generator during 100 hours per year, I would save less than 2 euros per year on our energy bill.

Still it was a fun project and I learned a lot from it, so I enjoyed it. And in the next months I plan to use it for some exercising when it is cold and rainy outside.