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Re: ISO: AC vs DC Project ideas
5 of 5 people found this helpfulmakerkaren First, we would want to get that AC down to a safer level. May I suggest a doorbell circuit? Rings on AC. EDIT: Also rings on DC.
Probably $20 at Menards for a wired doorbell kit.You could also do transformer down and back up with two doorbell transformers.
There is always the oscilloscope trace.
If you want to get really brave... 120v into a motor starting capacitor - to show capacitive reactance. Calculate the reactance. Apply Ohms Law. Use a splitter and a clamp meter to show the current flow. DC just charges and then current flow stops. AC just goes on - like Celine Dion's heart.
If you refine the target a bit, we might be able to get something spot on for you.
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Re: ISO: AC vs DC Project ideas
ralphjy
Feb 17, 2021 7:45 PM
4 of 4 people found this helpfulI think that simple front end circuits for power supplies would be a good illustration. You could use a step down transformer so you work with lower voltages. Maybe show the effects of full wave and half wave rectification.
Use of center tap transformers, etc. And the effects of filtering. Good to show waveforms on a scope.
Ralph
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Re: ISO: AC vs DC Project ideas
5 of 5 people found this helpful"...I have a bit of a conundrum. AC is not something to play around with casually. But I need a project to build for the follow-up episode to the lesson video. What do you think would be a good, safe project to demonstrate alternating current? Or to show off the difference of AC vs DC?..."
Perhaps could use the waveform generator on your scope for this.
As for a project why not build a circuit which generates a sine wave output:
https://www.nutsvolts.com/magazine/article/seven-common-ways-to-generate-a-sine-wave
Or perhaps take a look at some of the analogue synth type projects.
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Re: ISO: AC vs DC Project ideas
4 of 4 people found this helpfulWhat do you all think of using a motor to make a generator? I haven't looked into it much yet, so I don't know the details of how it would work. Has anyone done anything like that before?
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Re: ISO: AC vs DC Project ideas
3 of 3 people found this helpfulHand cranked magneto generator like the old telephones.
Car alternator attached to an exercise bike (with the rectifier bypassed).
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Re: ISO: AC vs DC Project ideas
3 of 3 people found this helpfulAnother DIY alternator link:
Rain Gutter POWER #2 - 3D Printed Alternator, BEST Explanation of a Rectifier EVER!!! - YouTube
(complete with flashing LEDs)
Could perhaps generate the AC, step it up through a transformer, step it back down through another transformer, then rectify it to DC. Plenty places to probe with your scope and talk about the theory along the way. Then there is always Three-Phase...
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Re: ISO: AC vs DC Project ideas
3 of 3 people found this helpfulSpotted this educational hand-cranked AC generator which may be of interest:
https://www.lascells.com/product-detail/a-c-generator/
It's good that you get to see the internals through the transparent window.
A gearbox on the input may be helpful to spin the magnet faster when hand-cranking. Alternatively drive it with a small motor.
( Cycling helmet and go faster Lycra optional with this one...
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Re: ISO: AC vs DC Project ideas
Oo! That's really neat! I have a hand-crank flashlight, but you have to take it apart to see the mechanism and it has to be fully assembled before it works. I love when things have windows so you can see it work.
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Re: ISO: AC vs DC Project ideas
dougw
Feb 18, 2021 4:13 PM
4 of 4 people found this helpfulLots of industrial controls run off 24 Vac (partly because it is safer) and you can get lots of wall-warts that output AC between 3Vac and 24Vac:
24Vac power24Vac power
24Vac fan24Vac fan
24Vac relay24Vac relay
Many thermostats run off 24 Vac.
Build an AC generator....https://www.youtube.com/watch?v=O5n6ubrbK5A
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Re: ISO: AC vs DC Project ideas
3 of 3 people found this helpfulSimple home door bells in north america run on AC. A 24VAC transformer is bolted to an AC wiring junction box and the 24V is taken to a button and used to drive the solenoid. Not that complicated.
You could also power a project from a AC adapter. The participate is completely isolated from coming in contact with the main power. AC is from the wall wart. I have a few motors that run on low voltage AC.
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Re: ISO: AC vs DC Project ideas
ntewinkel
Feb 18, 2021 4:36 PM
3 of 3 people found this helpfulSprinkler system valves tend to use 24 Volts AC.
Which also means the sprinkler system power supplies tend to be 24 VAC too.
One tricky bit about AC is that you can't just use the same transistor type setup as you might use to switch a DC motor on and off from something like an Arduino.
Relays work well, but otherwise you end up with a fairly complex bit of circuitry to switch AC, as I found out the hard way when building a board to work with OpenSprinklerPi several years ago
Best,
-Nico
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Re: ISO: AC vs DC Project ideas
Thanks for the ideas, folks! I'll have to ruminate on your suggestions. Feel free to post more.
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Re: ISO: AC vs DC Project ideas
shabaz
Feb 19, 2021 9:22 AM
4 of 4 people found this helpfulHi Karen,
Once you have a way to supply AC using the methods mentioned above (also there are some low-cost signal generators) then there's quite a few experiments that can be done to examine electronic components, which would be of interest to either high-school physics lessons, or for first-year uni. It is worthwhile for beginners to try such things because it gave quite a lot of insight into how components work. In brief, it involves connecting the AC source to any component in series with a resistor (ideally a resistance box or variable resistor), and then using a multimeter or two to see the voltages across the component and across the resistor. Adjust the resistor until both voltages are the same, and then plot that resistance on graph paper, for different AC frequencies. Anyway it's described in the writeup below (it's my uni lab notebook since I still have it), along with example plots for various components. When you combine a couple of components (R and C or R and L) then it gets interesting because then you can see the resonant frequency of that circuit.
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Re: ISO: AC vs DC Project ideas
6 of 6 people found this helpfulThese are safe AC generators and can be scavenged from old bicycles:
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Re: ISO: AC vs DC Project ideas
A normal bicycle? Or an e-bike? I don't think I've seen these on an old bike before. I know they can be used to power a light though.
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Re: ISO: AC vs DC Project ideas
fmilburn
Feb 22, 2021 10:34 PM
3 of 3 people found this helpfulThese were more common in Europe than the United States and are for regular bicycles. I haven’t seen one here in a while but I see they can still be bought on Amazon. A bike shop might have an old one. You could also look at crank flashlights. They may have rectification diodes but that could be removed.
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Re: ISO: AC vs DC Project ideas
4 of 4 people found this helpfulfmilburn I used the crank flashlights to demonstrate power generation to school kids. I removed the batteries so the flashlight only lights when you turn the crank. You can get the LEDs to glow dimly if you crank slow and they glow quite bright if you crank fast. I also sometimes pull them out when training generator service technicians to drive home the point of getting the engine running correctly before worrying about the generator/alternator.
For the kids, this makes electricity fun.
makerkaren This may not be applicable now, but you might find it useful in future episodes.
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Re: ISO: AC vs DC Project ideas
4 of 4 people found this helpfulmakerkaren wrote:
A normal bicycle? Or an e-bike? I don't think I've seen these on an old bike before. I know they can be used to power a light though.
They are so common here that I never imagined there would be a parallel world where they don't know them.
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Re: ISO: AC vs DC Project ideas
ntewinkel
Feb 23, 2021 1:56 PM
1 of 1 people found this helpfulI had one of those on my bike(s) when I was a kid in The Netherlands so I immediately recognized it
I did pick one up here in Canada at one point, but that little dynamo does add a fair bit of drag, and the hills here already hurt plenty, so I went back to battery power. With LEDs they last long enough anyway. plus we rarely go out biking at night - our area is just not set up for safe bicycle commuting.
Cheers,
-Nico
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Re: ISO: AC vs DC Project ideas
fmilburn
Feb 23, 2021 4:14 PM
The 3-speed Raleigh I had in England was equipped with one. Wish I still had that bike.
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Re: ISO: AC vs DC Project ideas
genebren
Feb 23, 2021 4:23 PM
I have had these on various bikes that I have owned (55 years ago) here in the USA. We had front and read lights on the bikes and some even had turn signals. What a blast from the past moment.
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Re: ISO: AC vs DC Project ideas
2 of 2 people found this helpfulThose are really neat. The only place I've seen one on a bike was when an energy company was using one in a demonstration for kids at a library. The kids could hop on a stationary bike and pedal to try lighting up different types of bulbs (incandescent, CFL, LED). If those were ever standard on bikes in the US, it's been a long time since that was the case. That's really cool that they were so popular in other countries though.
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Re: ISO: AC vs DC Project ideas
genebren
Feb 23, 2021 4:30 PM
3 of 3 people found this helpfulI am seeing some new ones listed on eBay for $5.95 and $3.45 shipping (from France).
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Re: ISO: AC vs DC Project ideas
2 of 2 people found this helpfulgenebren That's less than half the price they're listed for on Amazon (US). What's crazy is they're still available! They show the same kit I had on my bike 40+ years ago - with the big front light (small light, big reflector).
ntewinkel's comment on the drag brought back memories. Flipping that dynamo onto the wheel was like hooking up a load of bricks behind the bike.-
Re: ISO: AC vs DC Project ideas
genebren
Feb 23, 2021 5:03 PM
Very cool and very retro! My combo bike (street and trail) has battery powered lighting (I did some commuting on it for a while). I might have to convert it over to generator charged Li-Ion so I don't need to remember to recharge it (assuming that I fix the tires and tune it up a bit as it has been sitting in the garage for several years).
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Re: ISO: AC vs DC Project ideas
ntewinkel
Feb 23, 2021 5:15 PM
3 of 3 people found this helpfulgenebren wrote:
> I might have to convert it over to generator charged Li-Ion
Oh that would be really cool to implement as re-gen braking!
Press the brake handle to make the dynamo flip onto the wheel to slow you down while charging the battery
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Re: ISO: AC vs DC Project ideas
genebren
Feb 23, 2021 5:27 PM
That would be pretty cool! You might even be able to keep the generator engaged and just increase the current draw (batter charging current) to add braking (brake switch).
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Re: ISO: AC vs DC Project ideas
1 of 1 people found this helpful"...Oh that would be really cool to implement as re-gen braking!..."
Dynahubs may work better for that but then you are only one step away from an electric bike.
https://en.wikipedia.org/wiki/Hub_dynamo
Harder to retrofit though unless you enjoy basket weaving.
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Re: ISO: AC vs DC Project ideas
1 of 1 people found this helpful"...Flipping that dynamo onto the wheel was like hooking up a load of bricks behind the bike..."
A lot weren't aligned properly when fitted, causing a lot of unnecessary additional drag.
I recall the dynahubs were much better in that respect but not as commonly availably as difficult to retrofit.
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Re: ISO: AC vs DC Project ideas
3 of 3 people found this helpfulHow about something to do with homemade simple motors ?
2 pole machine - 4 magnets on a shaft/rotor , the stator coils get 5V DC and then AC using an variable frequency 5V supply ( signal generator ) or square wave generated by an Arduino firing an H bridge ?
