Pads for Vin and Gnd
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Al Grant 2 weeks ago
Hello, I am new to EasyEDA. I have had a go at creating my simple circuit I would like to print. A few issues I have not been able to get past, before I add the traces: My project is here : [https://easyeda.com/editor#id=5d1a3eaff18249d3a87c46eec56cec60](https://easyeda.com/editor#id=5d1a3eaff18249d3a87c46eec56cec60) I would like to add three pads for connecting the power wires : Vcc Low, Vcc High and Gnd - how to add these? In the schematic or in PCB layout and connect them to the voltage regulator? Many thanks in advance, Al
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deskpro256 2 weeks ago
Hi, the link doesn't work for me and if checking your profile, there doesn't seem to be a public project. Check again if you have it set to public. With the OSHW thing it has been a bit of a pain for me to just have the project public. Too many steps :D and many times it failed. But as for the question, if it is an integral part of the design, please do add it to the schematic first and the EDA will add it to the PCB after updating the PCB. Otherwise if you do add it just on the PCB layout, after updating the schematic, the pads could disappear. As the are just connections for wires, you can use the integrated libraries headers, as a single pad or 3 in a row. Here you can see I have done it for this switch: ![1.png](//image.easyeda.com/pullimage/Lu58Ti4SnidOgdjnjJjUA98lYXd8VY9WNtvmXefT.png) ![2.png](//image.easyeda.com/pullimage/SrDd5VdJE9q9ksnJ0IZ2YXQ9RD82srG7brvH1M8S.png) If necessary, you can also select the pads and change their shape, size, hole size for easier soldering. Hope this helps!
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andyfierman 2 weeks ago
As @deskpro254 says, setting up a public project on OSHWLab and sharing it is a pita. Here's a topic describing how to make a project public and share the links to it: [https://easyeda.com/forum/topic/How-to-make-a-Project-public-and-share-the-links-to-it-9f006513b84b412580910905b0281d20](https://easyeda.com/forum/topic/How-to-make-a-Project-public-and-share-the-links-to-it-9f006513b84b412580910905b0281d20)<br> <br> Check that the hole and pad diameters are suitable for the wire sizes you wish to use and, after doing **Update PCB...** or **Import Changes...**, adjust the pad sizes as suggested above.
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andyfierman 2 weeks ago
If you just want to solder wires to the board and don't want a connector to appear in your BOM, select the connector in the Schematic and set the **Add into BOM** attribute to **No**: ![image.png](//image.easyeda.com/pullimage/GcWGC9E9qazhugN7Vi7HntCkq05SDbmrDO5qwKGd.png) This is explained in more detail in Appendix A of (2.2) in (2) in: [https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a](https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a)<br> <br>
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Al Grant 2 weeks ago
Awsome - thank you for the answers. Try this link by the way: [https://oshwlab.com/bigal.nz/new-project](https://oshwlab.com/bigal.nz/new-project)<br> <br> I have just added the pads to the pcb layout - but as pointed out this may not be the best way. If the link works and there is any further suggestions please let me know. Its very simple project, but if it ships ex china I would like to get it right :-) Thanks Al <br> <br>
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Al Grant 2 weeks ago
Something like: ![image.png](//image.easyeda.com/pullimage/laZkH367DlS9UhBJigv0rsMmMAks0SeWnBMbsAQu.png) for ![image.png](//image.easyeda.com/pullimage/fYBmwOSxKbfC7iFiB8fdyIsL21dCv1tgVC8exVd3.png) Can you label the lins?
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andyfierman 2 weeks ago
@bigal.nz, Your link gets me to the page in OSHWLab but it won't open into EasyEDA. Some comments. 1. Those LED symbols are unnecessarily huge and unhelpful. They could just be an ordinary LED symbol;  2. You have no supply decoupling capacitors at the input or the output of the 7805. Please read the device datasheet for decoupling advice and: [https://easyeda.com/forum/topic/UPDATED-Power-supply-decoupling-and-why-it-matters-30a39d0a77f34d5d8dc77e37c035b3d3](https://easyeda.com/forum/topic/UPDATED-Power-supply-decoupling-and-why-it-matters-30a39d0a77f34d5d8dc77e37c035b3d3);  3. Unless you intentionally want to have very little light generated by these LED arrays, the 5V output from a 7805 is not going to work well. These arrays need somewhere between 9V and 36V to drive them. Here is a commercial driver specifically designed for such devices: [http://www.powerint.com/sites/default/files/PDFFiles/der387.pdf](http://www.powerint.com/sites/default/files/PDFFiles/der387.pdf);  4. What input voltage are you supplying to the 7805 and how is it derived? From your OSHWLab comment of "Convert CFL to LED" it might be assumed that you are expecting to apply a mains supply to it? 5. The tracks on your PCB are far too narrow for the currents that these LED arrays can draw with an appropriate driver;  6. These LED arrays require significant heat sinking which your PCB does not appear to provide. Please read: [https://cree\-led\.com/media/documents/CXA\_design\_guide\.pdf](https://cree-led.com/media/documents/CXA_design_guide.pdf) [https://cree-led.com/media/documents/XLampThermalManagement.pdf](https://cree-led.com/media/documents/XLampThermalManagement.pdf) [https://cree-led.com/media/documents/ds-CXA1304.pdf](https://cree-led.com/media/documents/ds-CXA1304.pdf) [https://cree\-led\.com/media/documents/CXA1304\_GU10\_ref\.pdf](https://cree-led.com/media/documents/CXA1304_GU10_ref.pdf)<br> <br> <br> <br> <br> <br> <br> <br>
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andyfierman 2 weeks ago
@bigal.nz, "Can you label the lins?" Net label. [https://docs.easyeda.com/en/Schematic/Wiring-Tools/index.html](https://docs.easyeda.com/en/Schematic/Wiring-Tools/index.html)
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Al Grant 2 weeks ago
@andyfierman I used those LED symbols because they match the part I want to use and didnt know any better. It was a user uploaded part. The 7805 isnt what I am using - I am using a LM2940T. Sorry first go again. Input supply is 12v DC on pin 3 or 2 (depending on position of external switch). What track width would you suggest for a Cree LED? Can the head sink be addressed by a large pad, or do you think glue in a heat sink computer CPU style (but smaller) Thank you for helping! [https://easyeda.com/editor#id=5d1a3eaff18249d3a87c46eec56cec60](https://easyeda.com/editor#id=5d1a3eaff18249d3a87c46eec56cec60)<br> <br> [https://oshwlab.com/bigal.nz/new-project](https://oshwlab.com/bigal.nz/new-project)
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andyfierman 2 weeks ago
The lowest forward voltage version of the CXA-1394 LED array is 9V so unless you are using the LM2940T-9 or LM2940T-10, you are wasting your time since the LEDs will emit little more than a cheery glow. The LM2940T is limited to 1A output so at most you will drive 1A into a single LED or a very badly controlled 0.5A into two in parallel (see [https://easyeda\.com/andyfierman/LEDs\_must\_have\_series\_resistors\-OoGYgCK2k](https://easyeda.com/andyfierman/LEDs_must_have_series_resistors-OoGYgCK2k)). So the track width must be able to carry at least 1A with negligible voltage drop and temperature rise. There are several posts about online track width vs. current vs. temperature rise. I could not comment on heat sink size and attachment since this needs to be carefully  calculated and at the moment there is insufficient information about your application to do that. Sorry but the design of high power LED circuits and drivers is not simple and is hard to get anywhere near right without a thorough understanding of the issues involved. You can probably make a nice bright led lamp replacement but it is very unlikely to be reliable. You need to write yourself a Design Requirements Specification and do the sums to work out power dissipations and find of about thermal resistances of the different options on how and to what you can attach the led arrays. The links I have posted earlier will be of some help.
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Al Grant 2 weeks ago
It is the LM2940-T with 12v going in. Yes limited to 1A. I have estimate a conservative 2A should require about 1.1mm in trace width (internal). I am actually not designing the circuit but copying another circuit - so I am lead to believe the design is tested. If you will take a PM would you consider a paid review of the project? <br> <br>
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andyfierman 2 weeks ago
@bigal.nz, Certainly. You can contact me via enquiries @ signality.co.uk
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Al Grant 2 weeks ago
It says after 24 hours email undelivered but will keep trying? Incidentally I breadboarded the project. Those Cree's get really really hot fast. I see why you need a large HS.
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andyfierman 2 weeks ago
@bigal.nz, Sorry about that, sometimes happens, no idea why. Try andyfierman @ signality.co.uk You said you are using the LM2940-T but you have not said what output voltage version it is.
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Al Grant 2 weeks ago
@andyfierman LM2940-T10. Will try email. Going to have to redesign so that the LM2490-T in TO-220 is on the edge of the PCB and can have the base plate bent over and screwed into the Heat Sink.
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andyfierman 2 weeks ago
What's the voltage drop across each of the two 0.56 Ohm series resistors?
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andyfierman 2 weeks ago
What voltage variant of the CXA1304 LED array are you using?
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Al Grant 2 weeks ago
@andyfierman [https://nz.mouser.com/ProductDetail/cree-led/cxa1304-0000-000c00a40e8/?qs=vvQikfcDqaVAWm5x4AvVTQ==&countrycode=NZ&currencycode=NZD](https://nz.mouser.com/ProductDetail/cree-led/cxa1304-0000-000c00a40e8/?qs=vvQikfcDqaVAWm5x4AvVTQ==&countrycode=NZ&currencycode=NZD)
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Al Grant 2 weeks ago
@bigal.nz I will measure the voltage drop when home next.
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Al Grant 2 weeks ago
Last email bounced again - but here is my reply: Right.... But the reason I have never questioned the components too much ( actual heat sink aside) is that these are the exact components the company that make the lights use in there upgrade kits, and they have sold lots. Temp wise on boat, maybe 10C to 30C. Not much condensation, but yes salt air.
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andyfierman 2 weeks ago
Replied to you by email.
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