Strong Magnet or Advice for school project

[namsu99]

Hey all. Assalam Alaikum.

Ive got this university project where I have to make a flashlight which charges when you shake it.
I thought of coiling wire around a coke bottle or a piece of PVC with a strong magnet inside it.

Shaking the bottle would move the magnet, inducing an AC voltage across the coiled wire.

Im having trouble finding a magnet to use. The ones I have at home - most of which were taken out of speakers etc - have a very weak magnetic field [around 0.002T]. A lot of people on the internet have used Neodymium magnets for projects like these - which are quite strong. Only, I cant seem to find them anywhere. The online shops which have them in stock, have listed them for about Rs 500 - 700, which is really expensive for a stupid project.

Is there any other type of magnet that I could use?
Or any changes I could make to my idea so that it doesnt require a very strong magnet?

@Newton [MENTION=12579]Shary Bhallu TC[/MENTION] and any other electrical/electronics engineers on PG!

 

[Shary Bhallu TC]

If you have some old corrupt or unsalvageable HDD laying around, you can extract a strong magnet from it. This method can work, you just need a strong magnet and if you are a little bit adventurous, you can attach a bridge rectifier (10-20 rupees or so from Sir Syed University) to the output of the coil to change that AC voltage into DC, and attach a 2200uF capacitor (not sure if need higher or lower capacitance) to make the output really amazingly good.

 

[Cerberus]

know of heatgun? people use these days to get high pressure gas
go to anyone heatgun repairer. and ask for heatgun magnet. it will work I think

 

[Newton]

your idea is correct, the concept is called faradays flashlight

you can find really strong magnets in vacuum cleaners

i know places in lahore where you can buy such stuff but dont know anything about khi

 

[namsu99]

[MENTION=12579]Shary Bhallu TC[/MENTION]
I don't have any old HDD around. I do have an old tape recorder and radio though. I already took out its speakers. Think there's something in that which might help me out?

Oh and yeah, I already have made a bridge rectifier and I plan on using a 1F, 5V capacitor as a battery as well!
If only I could fine a decent magnet!

[MENTION=26661]Cerberus[/MENTION]
No bro, I have absolutely no idea what a heat gun is. Any idea where I can find such a guy in Karachi?

[MENTION=12105]Newton[/MENTION] Vacuum cleaners? Amma maar dalein gi >.<
Do you have an idea about how much these strong magnets would cost?
Abhi abhi I called a shop and the shopkeeper referred me to another shop which he thinks might have them in stock. I'm going to check it out on Monday, inshaaAllah.


Jbtw, Can I increase the number of turns to compensate for a weak magnetic field?

 

[Cerberus]

this one.

 

[namsu99]

^I'll check it out tomorrow.
Thanks.

 

[Cerberus]

you can go to mobile repairing shop, they will guide you where to get one
or check out pawn shops

 

[namsu99]

So I got a magnet from Sadder.

They are really really expensive! This little piece cost me Rs 350!

The two lighter ones on top are neodymium. The larger one on the bottom is I dunno what. And I think it's losing its magnetism.

I got about 25 m of magnet wire and wound it around a 3.5'' PVC; which gave me about 227 turns. (didn't actually count the turns, did basic math [emoji14])

Anyway this setup is just giving me about 0.2V.
0.5 if I shake it really really hard.

I know I have to either increase the number of turns or get a stronger magnet, and since the stronger magnet is out of my budget, I think imma go with more wire.

Which leads me to my question. Can I connect two pieces of magnet wire in a coil? I've already got 25 m rolled around the PVC and have another piece, about 10 m long, lying around. How about I just join em both together and wind them. I know the 10 m won't be enough, but if joining them works, I'll buy some more and then join that too.
What do you guys say? [MENTION=26661]Cerberus[/MENTION] [MENTION=12105]Newton[/MENTION] [MENTION=12579]Shary Bhallu TC[/MENTION]

 

[Shary Bhallu TC]

One thing I need to know is that is the wire you wound on that tube insulated? It seems to not be insulated. :/ If it isn't insulated, this method wouldn't work.

 

[namsu99]

Yeah it's insulated.
I've just burned off the insulation off a small bit at the ends where I join them and where I connect it to the ends of the circuit.

It's magnet wire, so it doesn't have that coloured rubber insulation which is usually on jumper wires.

 

[Cerberus]

go for a single larger magnet. you cant just induce so much with increase no of turnings

 

[namsu99]

I searched the entire cooperative market, Sadder.

There was only one shop by the name of 'Sind Radio' which had magnets in stock. Nearly all the other shopkeepers told me to go there when I enquired about magnets. They said that's the only shop which has em.

Acha even Sind Radio didn't have proper magnets. What they had were either odd pieces of broken magnets from speakers, hard drives etc or small disks of neodymium magnets (of which I bought two). Plus they were expensive as well.

Did you see the small disks magnets in the picture above? Well the guy had a stronger type of that as well. And he was selling it for Rs 800. That one small disk which had a thickness of about half a centimeter and wasn't bigger than a five rupee coin. It was stronger, but not by much. I doubt it would've been able to produce a strong enough magnetic field.

Besides that I checked some other shops in Gulshan, behind Sir Syed university all of which told me to go to Sadder.

How is it possible that it's so difficult to find a decent magnet in Karachi.

Ya tou mein Sahi se market nahi ghoom raha. :/

 

[haroonshaikh]

I bought once strong magnets that were extracted from HDD from shershah.
Have to check if i still have them. will let u know and you can pick it from me for free

 

[haroonshaikh]

Ok found my magnets. These are small but extremeley powerful (if you get them stuck to each other, really hard to separate them). They are so powerful that they attract to each other with such force, that they break with the impact.

I got these 7 years back from shersha for a project of mine. i was making a tesla turbine.
Here is a link what i wanted to make
Build an Amazing Tesla CD Turbine

However, i got carried away in other projects and never completed it. so its lying since then half completed. as of now i have 20 of these attached to the CD's (they can be removed from the CD, were attached with glue) plus 1 separate magnet. I am providing the link for the pictures as well. Let me know if you want these, if yes you can have them for free. Since you are a student, i dont expect you would be having a car. so PM me your location and ill see if it falls in my route to office then ill drop it off at your home or you can pick it form my home. Whatever suits you best

link of pics of magnets
Magnet Photos by haroonshaikh | Photobucket

 

[namsu99]

I forgot about this thread lol!
Anyway I got the Flashlight working.

Got two small neodymium magnets from cooperative market, Sadder and loads and loads of wire (around 60m).