Inductors or solenoids??? - Page 1
Forum section: electronics / projects

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 10:07:36 pm
content: HelloRecently a teacher at my school let me get 2 "broken" pcs (only bad power supplies) and their motherboards have some good caps , some leds, some piezos and something that seem to be inductors but i dont think they are.........I would like to know if they are solenoids of just inductors... and due to their strange shape how can i calculate the calue of these things?Here are some pics:PS : ill create another topic in the same section to show what i got from the motherboard number one and what is still on the motherboard.Thank you

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 10:22:52 pm
content: An inductor is a coil. A solenoid is a coil. "Solenoid" in electronics usually refers to one used to actuate some sort of moving device.Quote from: ChrisGreece52 on May 11, 2013, 10:07:36 pmIf they have cores (since you found them on a motherboard rather than in a radio/TV/similar, I will assume they do), the answer is "no", because the core has too strong an effect. Look at W2AEW's most recent video for a good way to make a quick inductor measurement.

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 10:27:17 pm
content: You need to work on your image posting.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 10:28:35 pm
content: Quote from: c4757p on May 11, 2013, 10:27:17 pmLol i am sorry but you are right !!! what would you suggest ?? i upload the images to imageshack.us and then i post the direct link here .... [img link here

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 10:29:58 pm
content: Shrink them! And preview before you post. I just shrink my pictures to no more than 800x600 and upload them as attachments.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 10:31:39 pm
content: ok got it my resolution is high ..... i went with 1650X1050 ......but ..... as attachment you said ..... how

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 10:35:23 pm
content: Like this.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 10:41:45 pm
content: well thank you ( i did not even notice)

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 10:43:44 pm
content: You are welcome.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 10:50:40 pm
content: Quote from: c4757p on May 11, 2013, 10:43:44 pmbut anyway can i use them as inductors (till my 100uh ones arrive )

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 10:52:09 pm
content: They're most likely a bit low in inductance, so they might not do much good. Worth a try, though, and check out that video I recommended.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 10:58:08 pm
content: Quote from: c4757p on May 11, 2013, 10:52:09 pmfirst i will give iit a try.Second ... i dont know how to hook them up without causing a short. (i tried using one 470 ohm resistor in series with the inductor so it reduces current flow but .... how can i Visually inspect the effect of the inductor ?)and third .. what video ?

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 11:00:37 pm
content: Quote from: ChrisGreece52 on May 11, 2013, 10:58:08 pmQuoteWell... you don't just "hook them up". They're inductors, not mobile phones. What are you trying to do with it?QuoteYour Google broken?

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 11:04:44 pm
content: Quote from: c4757p on May 11, 2013, 11:00:37 pmQuoteA basic circuit to learn something practical about inductance i think that a battery in series with a resistor an led and an inductor will do the best example .... (my knowledge of inductunce so far is only theoretical and comes only from school)QuoteNo but the way you said it implied that you had already sent me a video

author: TerminalJack505
author_rank: Super Contributor
timestamp: May 11, 2013, 11:05:08 pm
content: He's talking about this video:http://youtu.be/74fz9iwZ_sM

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 11:06:14 pm
content: Quote from: ChrisGreece52 on May 11, 2013, 11:04:44 pmI said "W2AEW's most recent video". Google "W2AEW" and click the first thing you see.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 11:09:48 pm
content: Quote from: c4757p on May 11, 2013, 11:06:14 pmThats why i reffered that i instanlty forget things

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 11:11:32 pm
content: Quote from: ChrisGreece52 on May 11, 2013, 11:09:48 pmI am well known in my family for going in a room to get something, them promptly returning to try to figure out what I left to get. My memory isn't bad, it simplydoesn't exist. Still, if I've got it written on a piece of paper I read the paper again before I go asking...

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 11:12:38 pm
content: Quote from: c4757p on May 11, 2013, 11:11:32 pmRight those sticky notes saved my life!!!

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 11:16:12 pm
content: Quote from: ChrisGreece52 on May 11, 2013, 11:04:44 pmIt's not going to do anything interesting. The basic equation for an inductor is v = L di/dt. di/dt refers to the rate of change of the current, and the only time the current is changing in that circuit is in the instant you connect the LED to the battery. Once the changing current settles down, the entire "L di/dt" term goes away and it becomes just a funny-looking wire.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 11:19:13 pm
content: Quote from: c4757p on May 11, 2013, 11:16:12 pmIf i use a 555 timer chip i will get a sawtooth wave as my physics proffesor suggested me to do he said that i i kept turning the switch on and off quickly enough i could create this wave

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 11:21:10 pm
content: Yes, you can definitely do interesting things with a 555 and an inductor.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 11:23:45 pm
content: Quote from: c4757p on May 11, 2013, 11:21:10 pmIll search for some schematics

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 11:26:02 pm
content: If it says "high voltage", anything like "Nixie", "flyback", or "arc", or has any numbers with more than two digits ending in a "V", please, for the love of God back away from the circuit.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 11:26:06 pm
content: Found these 2

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 11:27:05 pm
content: Quote from: c4757p on May 11, 2013, 11:26:02 pmi did not get that sr.....but why ?

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 11:27:12 pm
content: Oh dear Mary mother of.... add "mains" to the above list.

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 11:29:29 pm
content: Because you will toast your ass.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 11:30:59 pm
content: LOL thanks i will but the first one seems ok right ?

author: c4757p
author_rank: Super Contributor
timestamp: May 11, 2013, 11:33:43 pm
content: The first one seems OK, but it's still a boost converter, so you may be able to give yourself a bit of a small zap off it if those LEDs aren't there to clamp the output voltage. You still won't die. It should be reasonably save unless you go mucking about with the voltages and component values. Note that I've successfully used almost the same exact circuit, with just a few modifications, to convert 12V into 300V at enough current to cook you. Inductors always have the potential (heh.) to be unsafe because they can "generate" voltage.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 11, 2013, 11:36:22 pm
content: Quote from: c4757p on May 11, 2013, 11:33:43 pmOK ill keep searching

author: JackOfVA
author_rank: Unknown
timestamp: May 12, 2013, 01:30:00 am
content: In the radio side of engineering, a solenoidal inductor means one that is wound around an open, straight core, which may be air (if the wire is large enough diameter to support it) or plastic or ceramic or similar material, or a magnetic rod core. Its purpose is to act like an inductor, e.g, in a tuned circuit or to provide inductive reactance where DC may need to pass but AC signals need stopped (RF choke is one example.)In industrial electrical work, or automotive use amongst others, a solenoid means a mechanism whereby a electromagnet pulls (or, less commonly, pushes) an armature. Its purpose is to convert electrical energy to a mechanical action.Also in automotive use, a high current rated relay used to connect the starter motor to the battery is often called a solenoid instead of a relay.These terms are widely used in American engineering use, but I don't know if the UK or Australia have different words.

author: c4757p
author_rank: Super Contributor
timestamp: May 12, 2013, 01:32:35 am
content: Quote from: JackOfVA on May 12, 2013, 01:30:00 amAutomotive didn't even occur to me. They seem to have invented a completely different set of terms for just about everything...

author: IanB
author_rank: Super Contributor
timestamp: May 12, 2013, 01:42:01 am
content: A solenoid means an electromagnet designed to pull some kind of iron bolt or plunger. I didn't even know there was another meaning out there...

author: c4757p
author_rank: Super Contributor
timestamp: May 12, 2013, 01:45:42 am
content: The relay that switches the starter motor in a car is indeed routinely called the "start(er) solenoid". I suppose they needsomename for it - I know at least in my car, the coil current of this beast is so high that it is itself switched by a smaller relay! Which one is the "starter relay"?I guess the coil in a relay technicallyisa solenoid, but I kind of thought we agreed to call it a 'relay' when the thing it moves is an electric switch!And the all-knowing Wikipedia confirms that it does not have to move anything at all to be a solenoid.This was new to me too, actually. I double-checked before attempting an answer. Didn't remember about the automotive one though.

author: IanB
author_rank: Super Contributor
timestamp: May 12, 2013, 02:10:40 am
content: I quickly checked Wikipedia, but it affirms the main principle. The primary purpose of a solenoid is to generate magnetism, not to have inductance. In essence, a solenoid is aphysicaldevice, not anelectronicdevice. This is true even if the magnetic field is not immediately used for any specific purpose.

author: c4757p
author_rank: Super Contributor
timestamp: May 12, 2013, 02:15:48 am
content: Quote from: IanB on May 12, 2013, 02:10:40 amTomato, tomato.Er... that doesn't work so well in print.But yes, I agree

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 12, 2013, 03:35:27 am
content: Quote from: c4757p on May 12, 2013, 01:45:42 amI thought the solenoid was the part that mechanically engaged the starter.

author: c4757p
author_rank: Super Contributor
timestamp: May 12, 2013, 03:41:17 am
content: You have a point - it often does both, though it varies from car to car. Mine is purely electrical with a separate, "automatic" mechanism to engage and disengage.

author: SeanB
author_rank: Super Contributor
timestamp: May 12, 2013, 09:02:06 am
content: So you have a Bendix starter, not too common nowdays except on smaller motorcycles. The most common now is the preengaged starter with overrun mechanism. There the solenoid engages the starter gear onto the flywheel before the starter is powered by a set of large contacts that only close when the gear is fully engaged. As the engine starts to spin up the gear can move faster than the motor can drive it because it has an overrun clutch that allows it to run faster than the shaft but not the other way.The Bendix uses a spiral cut keyway on the motor shaft. As the motor starts the inertia of the large mass gear cause it to move out and engage the flywheel. When the flywheel speeds up as the engine fires it pushes the gear back down out of engagement.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 12, 2013, 10:14:14 am
content: Quote from: JackOfVA on May 12, 2013, 01:30:00 amThanks for the information!!!

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 12, 2013, 10:17:28 am
content: Quote from: IanB on May 12, 2013, 02:10:40 amso an electromagnet could be also called a solenoid

author: AlfBaz
author_rank: Super Contributor
timestamp: May 12, 2013, 10:52:50 am
content: Quote from: ChrisGreece52 on May 12, 2013, 10:17:28 amYou can call it what you likeSo far we have inductor, relay, solenoid and now electromagnetA generalisation for each of them could be something like thisThey're all inductors, hell even a piece of wire has inductance but generally speaking when referring to an inductor, you are referring to a device that provides an inductance value and that inductance is affecting the electrical signal, by design or by frustrationA relay has a fixed core within a coil that when energised will attract an armature that does something, such as switch contacts and if the contacts are big enough you can call it a contactor.A solenoid will have a moving core. When the coil is energised the magnetism pulls a plunger into the coil, the plunger is usually attached to some mechanical actuator. In the case of a starter motor, it moves the starter motor's cog into the flywheel gear and makes a large contact to provide current for the starter motor. Starter motors are normally series motors who's terminating speed is when the armature throws the windings out in a big sparkly mess... So its good to have it not start until the cog is fully engagedAn electromagnet will generally have a fixed core and nothing else. When the coil is energised the core becomes magnetised and that's it. These tend to be DC only. Metal scrap yards tend to use them to pick up metallic waste. In steel making plants several of them are placed in a row to pick up large metal slabs. I'm sure the magnetic field generated by electromagnets have many more uses but in some instances they may be called something different again, such as field or winding...

author: mikes
author_rank: Regular Contributor
timestamp: May 12, 2013, 11:23:14 am
content: I'm surprised no one has mentioned that the "strange shaped" inductor is simply wound on a toroidal core. This is commonly done to prevent field leakage, the flux stays within the core.There's no way to easily calculate the inductance. It will depend on the permeability of the core. Toroid manufacturer's often color code the cores, but there's no standard for that. Coming off a PC motherboard, they could have been painted a certain color just to add bling.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: May 12, 2013, 11:27:03 am
content: Quote from: AlfBaz on May 12, 2013, 10:52:50 amTHANK YOU!!!

author: JackOfVA
author_rank: Unknown
timestamp: May 12, 2013, 03:01:49 pm
content: Quote from: mikes on May 12, 2013, 11:23:14 amAnd if it's a ferrite core, the ferrite mix may have been selected to provide high loss (low Q) if its purpose is to suppress unwanted high frequency noise, or EMI suppression as it's known. Using a high loss ferrite core for other purposes will lead to "interesting" results.My guess is that the toroid cores are EMI control devices, but it's certainly possible they are filtering inductors in the switching supply. These two uses have rather different core material requirements.