Electrical Engineering

5:23 AM

Hi everybody

1 hour later…

6:27 AM

morning

3 hours later…

9:37 AM

This is a 24V DC Motor Controller board:

Why did they use the 1uF cap on the left?

I thought those kind of caps were for AC applications :s

1 hour later…

Rocketmagnet

10:59 AM

Hello everyone.

11:38 AM

@Rocketmagnet Hey! Long time no see!

Rocketmagnet

Hey! How are you?

3 hours later…

2:19 PM

@abdullahkahraman Those style of caps usually have really good transient characteristics

@Rocketmagnet I'm fine, thanks! You?

@W5VO Oh, thanks.

or at least I've seen good ones in that form factor

high ripple current rating and such

@W5VO I see..

What do you think about the heatsinking? I couldn't understand how did they assemble this thing, what package are their MOSFETs

Here is an another product of them:

And this one looks very strange to me: dfrobot.com/index.php?route=product/product&product_id=796

@abdullahkahraman This one looks to be joining the heatsink to the copper pour on the bottom side

2:34 PM

@W5VO But how did they mount it?

@abdullahkahraman This one might be doing the same, or trying to attach to the top

@W5VO I cannot see any screws

@abdullahkahraman Thermal epoxy? you can't solder them

@W5VO Thermal epoxy, hmm, something that I'm hearing of for the first time.

@abdullahkahraman I've used conductive (thermally and electrically) epoxy before, but not for a heatsink (for various reasons)

2:38 PM

@W5VO It is not rugged?

@abdullahkahraman It's somewhat permanent ;)

@W5VO Oh! No!

@W5VO That means impossible servicing

but realistically, both those heat sinks are probably held on with epoxy

or some glue

@W5VO That is not an option for the card I'm designing.. I have to find an another solution

You might see if there is some conductive epoxy that can be chemically removed.

our stuff had some particular requirements, so there may be something better

2:44 PM

@W5VO But the chemicals and the epoxy would be expensive for me to get

but even then, it's not going to be a super effective heat sink

I thought of maybe adding some kind of heatsink and mounting it with about 4 screws to the PCB but the screws will have distance stuff on it so that it will stand about 7-8 mm above the PCB leaving space for SMD components

And I will mount TO-220 MOSFETs to the heatsink vertically.

Hmm, seems like they are called standoffs

lol, look I have great artistic skills

@abdullahkahraman that's going to be really poor performance if you bolt them to the side like that

I found out that 3M makes adhesive thermally conductive tape

with a variety of adhesion strengths

lol

I think IR makes a SMT FET with a metal case, which would give you good top-side cooling

digikey.com/product-highlights/us/en/…

2:57 PM

Oh, boy: digikey.com/product-search/…

@W5VO They are going to be obsolete soon if I recall correctly

Oh, no they aren't

most heatsinks have mounting holes in them from the factory

should be easy to mount

I've recalled this one. It is a Dual Direct-FET and will be obsolete.

@abdullahkahraman Well... 36 yards of tape is about 33m...

@whatsisname Most factories will add holes to their heat sink for you if you ask

@W5VO Which is 3300 cm

That means it adds about $0.3 - $0.4 to the PCB cost.

@abdullahkahraman so you could do maybe 3k devices?

it's 2.54 cm wide, which is probably bigger than what you need

3:02 PM

@W5VO One PCB includes 4 MOSFETs

@abdullahkahraman digikey.com/product-detail/en/LI98-1120-12-0.15/1168-2058-ND/…

@W5VO Nice

Sup fellas

@Funkyguy Heya

I still cannot trust its ruggedness

Probably my dad will decide on something very old school and will make the PCB huge and will say "Well, this is the way we do things."

3:35 PM

Whoa, that Dual fet is kinda....funky

I mean, it has high resistance and gate capacitance

oh wait resistance isn't so bad

2 hours later…

5:16 PM

Question asking seems to be slowing down, at least by new users

5:30 PM

@Funkyguy How are you shannon?

@ThePhoton Hi, are you there?

@Roh more or less

@ThePhoton I have a question. in your opinion Which is correct or better?:

"How can I create an educational topic?"

"How can I make an educational topic?"

@Roh What's the context?

Q: How can I create an educational topic?

How can I make an educational topic? (e.g. when I have made a successful finished project and I want to share it with the others) Is there any feature to do that?

feature-request

Like a question for meta?

I think they both sound a little bit off, for a native english speaker. They're about equally bad, though. And I don't have any trouble understanding what he's asking, it just doesn't sound quite right either way.

Mostly because you can't "create" a topic. You create a post, or a tag, or a category.

5:46 PM

@ThePhoton But a topic is a type of post. isn't it?

A topic is what a post is about. On some BBS's, a topic is a group of posts, but I haven't seen it used that way on SE.

If he meant it as a group of posts (like on a BBS), then it's okay.

And I don't see any difference between "make" and "create".

@ThePhoton Ok, Thanks.

Have a good time, western hemisphere!

خداحافظ تا فردا

6:02 PM

morning

6:13 PM

@jippie Aloha

@ThePhoton ¡hola!

Aw man it is a tired day

@jippie Das kamm mir spanisch vor.

@ThePhoton well that is what a Chilean girl can do with a boy like me

DEUTSCH IST DIE BESTE!

6:21 PM

@jippie No bragging on chat.

@Funkyguy You've solved the "German capitalizes things weird" problem.

@ThePhoton Yup! capitalize everything. never wrong.

So any low hanging high rep answers left for me?

@jippie You missed the "please interpret the part number suffixes for me" one.

@ThePhoton the MOV / inductor / capacitor question?

ah shm is apparently a manufacturer of capacitors.

6:42 PM

good morning!

Would a question about how to build a load cell or strain gauge be on-topic on EE?

7:13 PM

a what?

A load cell is basically a sensor that measures force, and a strain gauge is one used to measure deformation

I'd say that they are just barely on topic

depending on your application

@Christoph I don't think it's a bad question, but it might fit better on physics.SE. I assume you're asking about what's the mechanism that makes a load cell work.

I know how a load cell works. My aim is to build a low-cost load cell (or a strain gauge that I can turn into one) for up to about 50 kg weight. It should have low drift and I could integrate a thermocouple for temperature compensation

can't you get load cells for pretty cheap though

7:21 PM

not ones with low drift it seems

they should be able to operate under load over a period of a year or even more

i think if it was simple to build one yourself for low cost, there would be products on the market

that tends to be true but it's not always the case