Looking for someone to design double sided board for me!!! - Page 1
Forum section: electronics / general

author: jimdt7
author_rank: Contributor
timestamp: June 10, 2014, 01:36:24 pm
content: Hello my friends,I have a project that I would like to complete this summer and it requires some eagle board design skills which I certainly don't have. Its a small two-layer board probably 12x12mm and all components are SMD. Is anyone willing to help me?Have a nice day,Jim

author: senso
author_rank: Frequent Contributor
timestamp: June 10, 2014, 07:52:34 pm
content: Something that small can't have much electronics, so, do you have a schematic of what you want to do?If so, post it here, leave some links for what ic's/packages you want to use and I can help you.

author: rob77
author_rank: Super Contributor
timestamp: June 10, 2014, 08:47:40 pm
content: apparently it's a very simple device according to the dimensions.. i would call it a great opportunity for You to learn PCB design

author: miguelvp
author_rank: Super Contributor
timestamp: June 11, 2014, 07:56:37 am
content: I will recommend this:https://www.sparkfun.com/tutorials/108https://www.sparkfun.com/tutorials/109https://www.sparkfun.com/tutorials/110

author: Wilksey
author_rank: Super Contributor
timestamp: June 11, 2014, 12:47:59 pm
content: As people have mentioned, you need to provide a schematic or at least a clear sketch of what you want to achieve.

author: Bored@Work
author_rank: Super Contributor
timestamp: June 14, 2014, 03:34:47 pm
content: Why don't you just buy a buck converter on ebayeBay auction: #400597536264? I mean, if it is a project you anyhow don't want to do on your own you can spend $1.82 and be done.Unless, of course, this is some kind of homework and you want to pass the work of others as your own. The polite description for this isacademic dishonesty. Your school probably has a web page with more details about this.

author: FrankBuss
author_rank: Unknown
timestamp: June 14, 2014, 03:56:09 pm
content: What IC do you use? The COMP and FB connections don't look like the image from the datasheet.

author: madires
author_rank: Super Contributor
timestamp: June 14, 2014, 04:19:37 pm
content: It's a constant current buck converter for LEDs. So you have to give it feedback about the current through the LEDs, i.e. adding a sense resistor as shown in the datasheet. The datasheet also explains how to calculate the sense resistor. Pulling down the FP pin to ground opens the control loop and the buck converter will try to push as much current as possible, and sooner or later it will let the magic smoke out.

author: Bored@Work
author_rank: Super Contributor
timestamp: June 14, 2014, 04:31:53 pm
content: Quote from: jimdt7 on June 14, 2014, 03:43:24 pmYou still haven't got it. There is no point asking people for favors to do your project, if you can buy it for peanuts. It's not much of your project if others are doing it for you.

author: FrankBuss
author_rank: Unknown
timestamp: June 14, 2014, 04:46:56 pm
content: Quote from: jimdt7 on June 14, 2014, 04:38:36 pmAs madires said: The datasheet describes it, and so does your very own image of the datasheet.Do you have any reason why you didn't use the COMP pin as described in the datasheet?

author: FrankBuss
author_rank: Unknown
timestamp: June 14, 2014, 05:28:45 pm
content: Why did you change C4? Now it is parallel to the LED, but that's not what the datasheet says.Did you read the datasheet or the explanation madires gave you for the FB pin? Should be not too difficult just to copy the "typical application circuit" from the datasheet.What does D1 do? If you want to protect it against wrong supply voltage polarity, it has to be in series.0 ohm resistors usually are used as easy to remove connections, if not needed, or not populated when mass produced. Again, the datasheet should tell you about why C5 is required or not. Frankly I'm not an analog expert, but I know that most of the time it is not a good idea to use a different configuration than what the datasheet says, unless you have a good reason to do so.

author: wraper
author_rank: Unknown
timestamp: June 14, 2014, 05:33:06 pm
content: Quote from: jimdt7 on June 14, 2014, 04:39:44 pmSo do you think that your non working schematic (FB pin) with IC designed for a different purpose will give you a better result? Where do you find anything about low ripple in the datasheet? Led driver obviously is not about low ripple. Don't know how you managed to push something reasonable out of it on your breadboard as switch will remain fully opened all the time with schematic provided. And seriously it is not a rocket science to get simple board out of Eagle, there are plenty of videos on youtube how to do it.QuoteI have no words.link to 100uf 25V @ DigikeyWhile I was writing this, you posted second schematic which is even more funny. Seriously just buy some module on ebay.

author: jimdt7
author_rank: Contributor
timestamp: June 14, 2014, 05:42:01 pm
content: That's why I came here in order for you guys to help me, I've read all posts but still cannot understand how the FB pin is connected....About the capacitor thing I was lookng for a ceramic one!

author: wraper
author_rank: Unknown
timestamp: June 14, 2014, 05:44:55 pm
content: BTW, now I'm not sure what you want to achieve? LED driver or step down converter? Anyway there are bunch of modules of both types. Otherwise start reading what is written in the datasheet and try to and take some time to learn Eagle.

author: jimdt7
author_rank: Contributor
timestamp: June 14, 2014, 05:46:39 pm
content: A buck led driver!Is it so hard to explain how it is connected? If it was so obvious (for me) I wouldn't be asking the same question again and again...and trust me I've read the datasheet many times!

author: wraper
author_rank: Unknown
timestamp: June 14, 2014, 05:47:45 pm
content: Quote from: jimdt7 on June 14, 2014, 05:42:01 pmWhy do you need ceramic if there are electrolytic on datasheet schematic with small ceramic in parallel.

author: jimdt7
author_rank: Contributor
timestamp: June 14, 2014, 05:48:50 pm
content: Quote from: wraper on June 14, 2014, 05:47:45 pmBecause I am looking for small size components!

author: rob77
author_rank: Super Contributor
timestamp: June 14, 2014, 05:52:15 pm
content: i think we should start ignoring this thread.the OP is constantly deleting posts - this thread makes no sense at all.if a thread is preserved without significant modification - then that thread have a value for other people - they can learn something from it. but this one is useless thanks to the constantly deleted posts.

author: wraper
author_rank: Unknown
timestamp: June 14, 2014, 05:53:38 pm
content: Quote from: jimdt7 on June 14, 2014, 05:46:39 pmThen why do you try to alter the readily available schematic in the datasheet without a smallest understanding what you are doing? Bored@Work was also confused and recommended that buck converter module because it seemed that you try to alter schematic for different purpose. So my recommendation - buy LED driver module or learn how to draw PCB layout and use standard schematic in the datasheet.

author: jimdt7
author_rank: Contributor
timestamp: June 14, 2014, 05:55:43 pm
content: Ok thanks again for your tip! One last time can you PLEASE explain how to connect the FB pin because as far as I can understand from the datasheet the fb pin goes to the resistor and then the resistor connects to GND...

author: gxti
author_rank: Frequent Contributor
timestamp: June 14, 2014, 06:00:12 pm
content: Nobody can help you because you deleted your posts. Good luck.

author: jimdt7
author_rank: Contributor
timestamp: June 14, 2014, 06:02:06 pm
content: Ok...

author: wraper
author_rank: Unknown
timestamp: June 14, 2014, 06:06:53 pm
content: Ok, I'll answer. FB pin isFeedback, it is needed to control current which flows through the LEDs. This is achieved by measuring voltage drop across the resistor connected in series with the LEDs. This is written in the datasheet BTW.

author: miguelvp
author_rank: Super Contributor
timestamp: June 14, 2014, 06:18:00 pm
content: Not sure about the sudden secrecy, but here is the datasheet in question, they do put a capacitor in parallel to the output.http://www.feeling-tech.com.tw/km-master/ezcatfiles/cust/img/img/24/fp7103v02-lf.pdfAnd the 2nd schematic he posted (now deleted) has the LED cathode hooked to the right place between FB and what was R1 on his schematic.

author: wraper
author_rank: Unknown
timestamp: June 14, 2014, 06:45:11 pm
content: Quote from: miguelvp on June 14, 2014, 06:18:00 pmHmm, it this datasheet, which seems to be later revision there is no cap except the first pagehttp://www.micro-bridge.com/data/Feeling-tech/FP7103.pdf. And on your's one it is marked as NC.

author: miguelvp
author_rank: Super Contributor
timestamp: June 14, 2014, 07:04:33 pm
content: Right, my bad for just taking a quick glance without even looking at the values.