Electronics basics

Thread Starter

JimZap

Joined Mar 30, 2020
19
Hi guys,

Hope you are all well and staying safe under the circumstances.

I am hoping I can get some help and advice on some electronics.

So I currently have 2 designs I'm playing with and want your opinions on parts and components to help these designs work as efficiently as possible.

So my first project is a miniature working circular saw, I aim for this to be fully functional and allow me to use it in my matchstick/woodwork hobby (which I also incorporate electronics with) I have a basic prototype that works but I know with a few tweaks I can improve it no end.

The circuit I am using has 1 x 4.5v lego motor, a basic switch I took from an led aquarium light, and a dremel 12v battery. So far it works ok and I will be rebuilding it using sturdier components ie metal spindles and bearings etc. As it stands too much resistance on the blade stops the motor turning, is this something I can avoid/improve woth electronic components?

The second project I am working on is a mobile phone docking station complete with speakers built in. I am building this out of wood and matchsticks and plan to embed the cables and components into it. I have found a smallish speaker but I'm ideally looking for speakers 15mm diameter. And also wanting to know what if any electrical components could improve this design. So far electrics wise it is just a charging cable and an audio cable linked to 2 speakers.


Thanks verry much in advance guys

Stay safe

Jim
 

Attachments

AlbertHall

Joined Jun 4, 2014
9,628
As it stands too much resistance on the blade stops the motor turning,
That sounds like the motor is not powerful enough for the job. Short of using a different motor, the only solution is to increase the voltage supplied to the motor but if you exceed the rated voltage it will reduce the life of the motor.
 

Thread Starter

JimZap

Joined Mar 30, 2020
19
That sounds like the motor is not powerful enough for the job. Short of using a different motor, the only solution is to increase the voltage supplied to the motor but if you exceed the rated voltage it will reduce the life of the motor.

Great stuff, I shall get a larger motor :)

As for the circuit I'm not missing anything am I?
 

ci139

Joined Jul 11, 2016
1,351
although the saw is miniature -- you should keep the same safety precautions as with the regular size tools . . . e.g. if you increase the speed and the blade or a bit of it flies off . . .

you should apply proportional to it's size less force while operating it . . . such things are likely sold . . .

. . . or then not exactly

( the ® searc ) https://www.youtube.com/results?search_query=mini+lathe+circular+saw+jig
▼▼ (not a match)
▼▼ (??? near match . . . as "anything so far" ???)
 

BobTPH

Joined Jun 5, 2013
2,346
A small saw has to spin faster than a large one. What matters is the speed of the teeth going across the wood. A 4 inch saw will have less than half the tooth speed of a 10 in saw at the same RPM.

Bob
 

Thread Starter

JimZap

Joined Mar 30, 2020
19
Wow those videos are great, I think I will work on that second one first as I have the materials mostly for that already. How easy would it be to modify the design to use a usb cable?

Thanks
 

Thread Starter

JimZap

Joined Mar 30, 2020
19
A small saw has to spin faster than a large one. What matters is the speed of the teeth going across the wood. A 4 inch saw will have less than half the tooth speed of a 10 in saw at the same RPM.

Bob
That's another good point, in my prototype I literally made a blade out of a tin can and gave it a lot of teeth for its size, seemed to work well with the motor and battery but then I decided to just buy some different sized blades to experiment with. I was originally looking at a 2 inch blade like you would find on a dremel. The blades I have seen for these seem to have a lot of teeth. I intended to use it mainly on matchsticks and lollipop sticks but seeing that video has made me realise that actually making a slightly larger design will allow me to use it to make other things as well.

Thanks for all the input guys ok really appreciate it
 

dl324

Joined Mar 30, 2015
10,493
As it stands too much resistance on the blade stops the motor turning, is this something I can avoid/improve woth electronic components?
No amount of electronics is going to make the motor be more powerful. Bigger motor or operate the existing one at a higher voltage; if allowed.
I have found a smallish speaker but I'm ideally looking for speakers 15mm diameter. And also wanting to know what if any electrical components could improve this design.
What is the speaker resistance and what are you driving it with? You could increase volume with an amplifier and adjust volume by varying its gain.
 

Audioguru again

Joined Oct 21, 2019
1,269
15mm is a squeaker, not a speaker. The speaker in a cheap clock radio sounds awful but is much larger at 75mm to 80mm.
Since you want two speakers then maybe your mobile plays music then you will need speakers that are at least 100mm.
Of course the speakers will need an amplifier.
 

Tonyr1084

Joined Sep 24, 2015
4,369
Just junked a flat panel TV. Kept the speakers from it. They're oval (rectangular) in shape and had pretty decent quality sound. But I don't know anything about the driver circuit for those speakers. And those speakers have been placed in a safe place, so I have no idea where they are right now. Otherwise I'd go have a look and see if there was information on them.

Yeah, a motor has limited power due to its size and speed. More voltage would spin the motor faster and with more power - but it could also damage the motor. Sounds like it was designed to work on 3 AAA or 3 AA batteries. The larger the batteries the longer the run time but NOT the greater the power. 4.5 volts is 4.5 volts. And the motors internal resistance (impedance) changes with the speed of rotation, but overall, basically it's a fixed value. Therefore Ohm's law will apply.

Assume 4.5 volts and 9 ohms. 4.5 volts divided by 9 ohms equals half an amp. Wattage is voltage times amperage, so at half an amp a 4.5 volt motor will produce 2.25 watts of power. Increase the voltage to 6 volts and here's the breakdown:

6V ÷ 9Ω = 0.67 amps (666 mA). 6V x 0.666 = 3.996 watts (4 watts) Almost double the wattage over the 4.5 volt power source. But also, almost double the heat being produced during operation. And if you bog down the motor - even more heat. I just don't see a lego motor surviving the project.

If you have a Dremel battery then don't you also have the Dremel? If you have that why not use that for cutting? It's already designed for the task. Larger than a lego motor I'm sure. But that's where you're going to have to go if you want a stronger cutting machine.
 

Tonyr1084

Joined Sep 24, 2015
4,369
Just contacted Xacto to see if they had a micro saw blade. They don't seem to. A hack saw blade cut down to fit into an Xacto blade holder might give you a nice hand saw for small projects. I can see wanting it motorized, but sometimes simpler is better.
 

Thread Starter

JimZap

Joined Mar 30, 2020
19
Just junked a flat panel TV. Kept the speakers from it. They're oval (rectangular) in shape and had pretty decent quality sound. But I don't know anything about the driver circuit for those speakers. And those speakers have been placed in a safe place, so I have no idea where they are right now. Otherwise I'd go have a look and see if there was information on them.

Yeah, a motor has limited power due to its size and speed. More voltage would spin the motor faster and with more power - but it could also damage the motor. Sounds like it was designed to work on 3 AAA or 3 AA batteries. The larger the batteries the longer the run time but NOT the greater the power. 4.5 volts is 4.5 volts. And the motors internal resistance (impedance) changes with the speed of rotation, but overall, basically it's a fixed value. Therefore Ohm's law will apply.

Assume 4.5 volts and 9 ohms. 4.5 volts divided by 9 ohms equals half an amp. Wattage is voltage times amperage, so at half an amp a 4.5 volt motor will produce 2.25 watts of power. Increase the voltage to 6 volts and here's the breakdown:

6V ÷ 9Ω = 0.67 amps (666 mA). 6V x 0.666 = 3.996 watts (4 watts) Almost double the wattage over the 4.5 volt power source. But also, almost double the heat being produced during operation. And if you bog down the motor - even more heat. I just don't see a lego motor surviving the project.

If you have a Dremel battery then don't you also have the Dremel? If you have that why not use that for cutting? It's already designed for the task. Larger than a lego motor I'm sure. But that's where you're going to have to go if you want a stronger cutting machine.
Yea the battery is the only part left, the machine itself broke (was also a poor copy of dremel lol) to be honest this is just as much a project to pass the time in quarantine as well as making myself something functional that I can use for further projects. I have all these tools already but I want to make my own miniature versions.
 

Thread Starter

JimZap

Joined Mar 30, 2020
19
As for the speakers, I'm wanting something that is no larger in size than 20mm x 20mm x 20 mm and I'm assuming it will need power as well as aux cable to be more powerful/better quality than my phone speakers?
 

Audioguru again

Joined Oct 21, 2019
1,269
20mm x 20mm x 20mm are earphones and will barely be heard.
Some computer speakers sound fairly good and come with an amplifier built-in. Mine are 900mm x 115mm x 120mm with 80mm speakers in them. Mine are powered from a 12VDC/1A wall-wart.
 

Thread Starter

JimZap

Joined Mar 30, 2020
19
Hi guys, so it's payday and I'm doing some shopping online for some bits and bobs. I'm trying to find the components for the circular saw video above. I have sourced all components apart from the 12-24V 5A power adapter.

Trying to source this from a UK seller, can anyone help?

Thanks
 

Thread Starter

JimZap

Joined Mar 30, 2020
19
15mm is a squeaker, not a speaker. The speaker in a cheap clock radio sounds awful but is much larger at 75mm to 80mm.
Since you want two speakers then maybe your mobile plays music then you will need speakers that are at least 100mm.
Of course the speakers will need an amplifier.
Thanks for the input, I've now changed my design as in the images. How simple can I keep this circuit? Based around a speaker 70mm in diameter as in the pics. Any advice here would be great. When u say an amplifier I'm assuming you don't mean a transistor? (Still learning)

Thanks again
 
Top