Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: Jdog on March 06, 2009, 07:00:40 PM
-
I'm brand new to eagle and I was hoping someone would be kind enough to check over my schematic. I added a Uart because I might as well. Any help would be greatly appreciated. I was also wondering if I had a good layout for the board, I haven't routed it yet, so it's just airwires.
EDIT:
I just realized I picked the wrong capacitor. Attached is the new schematic and board.
-
AREF and AVCC should both be connected to VCC
-
AREF and AVCC should both be connected to VCC
Thank you very much?
-
Hi,
I was also wondering if I had a good layout for the board, I haven't routed it yet, so it's just airwires.
How are anybody to judge your layout if you haven't routed your board?
The routing is a quite important quality in a layout (actually, you don't have a layout at all, until it's routed).
Please repost when you're done routing it.
-
Hi,
I was also wondering if I had a good layout for the board, I haven't routed it yet, so it's just airwires.
How are anybody to judge your layout if you haven't routed your board?
The routing is a quite important quality in a layout (actually, you don't have a layout at all, until it's routed).
Please repost when you're done routing it.
I don't really know why I asked about the board yet. I didn't want to bother routing it before I made sure the schematic was correct.
Heres the new schematic. Ill give the routing a shot now and then Ill post the board.
-
Hi,
You have a lot of junctions where you shouldn't and in at least one place you are missing a junction.
Don't draw wires across components.
Convention is: Positive voltages should be upwards, ground and negative downwards.
You have no capacitance on neither input nor output of the voltage regulator!
Using buses would clear up a lot of the wiring mess.
-
Hi,
You have a lot of junctions where you shouldn't and in at least one place you are missing a junction.
Don't draw wires across components.
I've never drawn circuit diagrams before so as long as it won't affect the final product right now, I'm not going to fix it because that means redoing the entire thing, but I'll remember that for next time.
Convention is: Positive voltages should be upwards, ground and negative downwards.
Once again, I'll remember for next time, but how can you tell the difference between downwards and upwards if it's just a vertical line.
You have no capacitance on neither input nor output of the voltage regulator!
I do have capacitance it's just right above the output bus, unless you mean putting it somewhere else, but the 220uf capacitor is connecting +5v and gnd.
Using buses would clear up a lot of the wiring mess.
I wish I would have known about busses when I made that. I just figured out what they are, and they would have saved me so much work.
Thank you for answering, sorry for my noobness.
EDIT:
Also, I took a shot at routing it. The leftover airwires I'll connect by wire. The weird thing is is that the voltage regulator doesn't have pads on it, so when I try to route a wire going to it, it turns red. I attached the board.
-
Hi,
Here is a schematic using buses to go on with if you like http://That.Homepage.dk/DL/50_board_2b2.sch (http://That.Homepage.dk/DL/50_board_2b2.sch).
I have changed the voltage regulator to a LM2940, since the one you used isn't through hole mounted and the LM2940 also has a lower dropout.
I have kept the terms Vcc and Gnd, even if they are incorrect, since it seems to be what people use here.
When using digital circuitry, the terms should be Vdd for positive and Vss for negative - Vss could be coupled capacitively to Gnd if wanted, while keeping conventions.
I changed your Supply label (named +5V) to B+, since the battery is not +5V (the Vcc line is, on the other hand).
Please check if I got any lines wrong.
I think some of my points will come through when you compare the schematics.
Your last board layout won't work with the screw terminals you have chosen. You have put them in a way that they occupy each others space on the board.
You have chosen screw terminals like the one shown here:
(http://farm4.static.flickr.com/3074/2967864740_ce810e5728.jpg)
Did you mean to use those, or did you just not find the pin-headers that most people use?
Pinheaders shown here:
(http://img.alibaba.com/photo/202512165/2_54_Pin_Header.jpg)
-
Firstly, thank you so much. I did mean to use the pin headers not the screw terminals. I understand the concept of busses but how did you make the circles that say vcc and things like that. I still don't know what you mean by
Convention is: Positive voltages should be upwards, ground and negative downwards.
.
Also I'm now in the process of checking it. When I do that I'll try the board and upload it.
EDIT:
I checked the schematic and I just have 1 problem with it. Why do you have 2 capacitors not included in the $50 robot schematic.
-
Better check for wire-codes on devices you want to attach or possibly going to attach.
You can create the busses according to these wire-colors , so devices can be attached without modifying the headers everytime.
This is a practical solution.
-
Hi,
I did mean to use the pin headers not the screw terminals.
OK.
how did you make the circles that say vcc and things like that.
They're in one of the "Supply" libraries.
I still don't know what you mean by Convention is: Positive voltages should be upwards, ground and negative downwards.
You noticed the circles "VCC", they're upwards while the ""GND"-bars are downward. Same with the polarized caps, + is up (unless special considerations dictates otherwise).
Btw. I had to turn one of your caps around, since it was connected in the "Kaboom direction".
I checked the schematic and I just have 1 problem with it. Why do you have 2 capacitors not included in the $50 robot schematic.
So that you won't have any problems with it ;D
Voltage regulators needs capacitance at both input and output (and physically close to the voltage regulator), or they will be prone to oscillations, which usually makes them either commit seppuko, or ghost some of the components it supplies.
-
Voltage regulators needs capacitance at both input and output (and physically close to the voltage regulator), or they will be prone to oscillations, which usually makes them either commit seppuko, or ghost some of the components it supplies.
What value range of capacitors should I use (I'm guessing somewhere between 150 and 250 uf)?
I also made the board design. Any feedback would be appreciated. Once again thank you so much for taking the time to help me. Also I'm wondering if I should make gnd and power polygons in the leftover space.
-
Stick with the original design 220mF - 12-16v, for the oscilator you can use 22 pF ceremic with A 16.000 OR 20.000 oscilator crystal.
-
I was following this tutorial on how to make it able to do by hand by adding the hobby.dru to the design rules, but when I make the board, I think the pads are too big and the drc says there isn't enough clearance between them. How could I fix this but still in a way that I can do it by hand?
Edit:
This is the tutorial, I forgot to post it.
http://www.instructables.com/id/Make-hobbyist-PCBs-with-professional-CAD-tools-by-/ (http://www.instructables.com/id/Make-hobbyist-PCBs-with-professional-CAD-tools-by-/)
-
Is it possible to drill out the holes for the components using standard settings without pulling off the pads by hand?
-
Is it possible to drill out the holes for the components using standard settings without pulling off the pads by hand?
what do you mean by standard settings?
-
Try this attached DRU:
http://www.instructables.com/file/FJ043CWRTMEP27Y3QS/ (http://www.instructables.com/file/FJ043CWRTMEP27Y3QS/)
-
Hi,
What value range of capacitors should I use (I'm guessing somewhere between 150 and 250 uf)?
I also made the board design. Any feedback would be appreciated. Once again thank you so much for taking the time to help me. Also I'm wondering if I should make gnd and power polygons in the leftover space.
Sorry for the delay, I made these files on the 10th. but forgot to upload them and then forgot about them due to some party arrangements I had to deal with.
http://That.Homepage.dk/DL/50_board_2b3.sch (http://That.Homepage.dk/DL/50_board_2b3.sch)
http://That.Homepage.dk/DL/50_board_2b3.pcb (http://That.Homepage.dk/DL/50_board_2b3.pcb)
They should tell you what you like to know.
-
Hi,
Stick with the original design 220mF - 12-16v, for the oscilator you can use 22 pF ceremic with A 16.000 OR 20.000 oscilator crystal.
220 mF (milliFarad) would be around 1000 times too large. ;)
(What do you americans have against using the correct "µ" symbol?).
No oscillator is used in this application.
If an oscillator was used there would be no reason for 22pF caps, as oscillators are complete circuits by themselves.
For a crystal, 22pF might be needed, but allways use the lowest capacitance that will start the oscillator reliably, as smaller caps equals lower deviation of the frequency.
-
Try this attached DRU:
http://www.instructables.com/file/FJ043CWRTMEP27Y3QS/ (http://www.instructables.com/file/FJ043CWRTMEP27Y3QS/)
I tried that originally, but when i did the drc it said there was not enough spacing between the pads.
-
Is it possible to drill out the holes for the components using standard settings without pulling off the pads by hand?
what do you mean by standard settings?
Hi, I meant the original settings that eagle had when I first opened it, before I loaded the hobby.dru file.
Hi,
Sorry for the delay, I made these files on the 10th. but forgot to upload them and then forgot about them due to some party arrangements I had to deal with.
http://That.Homepage.dk/DL/50_board_2b3.sch (http://That.Homepage.dk/DL/50_board_2b3.sch)
http://That.Homepage.dk/DL/50_board_2b3.pcb (http://That.Homepage.dk/DL/50_board_2b3.pcb)
They should tell you what you like to know.
The second link which is Im assuming for the board should have a .brd extension not .pcb and is therefore not working.
Hi,
(What do you americans have against using the correct "µ" symbol?).
It's not on the keyboard :P, although he should have at least typed uF not mF.
Also, just making sure, 220nF is the same as .22 uF right?
Edit:
Oops, accidentally double posted, sorry.
-
is there a way to add a key shortcut to type the µ symbol? eg "ctrl+y"
-
is there a way to add a key shortcut to type the µ symbol? eg "ctrl+y"
Only ones that will run programs: http://snarkhunt.blogspot.com/2005/04/dirt-cheap-macros.html (http://snarkhunt.blogspot.com/2005/04/dirt-cheap-macros.html)
But let's not get off topic. ;)
-
is there a way to add a key shortcut to type the µ symbol? eg "ctrl+y"
on mac you do Option+m
-
grrr, i dont use macs anymore :(
-
Hi,
http://That.Homepage.dk/DL/50_board_2b3.pcb (http://That.Homepage.dk/DL/50_board_2b3.pcb)
The second link which is Im assuming for the board should have a .brd extension not .pcb and is therefore not working.
It's not on the keyboard :P, although he should have at least typed uF not mF.
Also, just making sure, 220nF is the same as .22 uF right?
You saw it and yet you didn't just try changing the extension?
http://That.Homepage.dk/DL/50_board_2b3.brd (http://That.Homepage.dk/DL/50_board_2b3.brd)
Yeah, I just made the typo when I wrote it here, it's correct on the server of course.
Yes it IS on the keyboard, just hold down the right ALT (AltGr) and press "m" and you get "µ" (now there's no excuse anymore :P)
Yes, 1µ is 1,000n is 1,000,000p (and is 0.001m).
-
Hi,
Yes it IS on the keyboard, just hold down the right ALT (AltGr) and press "m" and you get "µ" (now there's no excuse anymore :P)
doesnt work on mine so i will continue to use uf hehe :P
-
Hi,
Stick with the original design 220mF - 12-16v, for the oscilator you can use 22 pF ceremic with A 16.000 OR 20.000 oscilator crystal.
220 mF (milliFarad) would be around 1000 times too large. ;)
(What do you americans have against using the correct "µ" symbol?).
No oscillator is used in this application.
If an oscillator was used there would be no reason for 22pF caps, as oscillators are complete circuits by themselves.
For a crystal, 22pF might be needed, but allways use the lowest capacitance that will start the oscillator reliably, as smaller caps equals lower deviation of the frequency.
Sorry Soeren , you are correct made a type over the capacitor. 220µF is correct. In the original design the internal oscilator will be used, but if you want more speed you could make holes/ connections for the crystal in advance. Yes if you look at (oscilator) crystel data-sheets 22pF will do fine. 18-30pF are acceptable for 16.000 -> 20.000.
-
You saw it and yet you didn't just try changing the extension?
http://That.Homepage.dk/DL/50_board_2b3.brd (http://That.Homepage.dk/DL/50_board_2b3.brd)
I was tired and wasn't really thinking. Any way, that board looks great thank you so much. Just wondering, would it be worth it to make power and gnd polygons, or would that be too difficult and unnecessary. Also how did you make the white lines showing that you would connect those by wire later, how did you make the mounting holes, or did you just use the hole button, and how did you have it displaying in a grid?
Edit:
I just noticed that you don't have ground on the board either.
Double edit:
I noticed you had a ground polygon mapped out but you didn't hit ratsnest to make it actually show as routed. That answers two of my questions. Also, how would I go about adding a silkscreen to a board?
-
Voltage regulators needs capacitance at both input and output (and physically close to the voltage regulator), or they will be prone to oscillations, which usually makes them either commit seppuko, or ghost some of the components it supplies.
Why doesn't the original $50 robot board design have capacitors at both in and out of the regulator?
-
i dont really know, i think it was because there wasnt to many servos going to draw much power. you could throw one in there if you wanted to i suppose.
-
Voltage regulators needs capacitance at both input and output (and physically close to the voltage regulator), or they will be prone to oscillations, which usually makes them either commit seppuko, or ghost some of the components it supplies.
Why doesn't the original $50 robot board design have capacitors at both in and out of the regulator?
I was being lazy and it worked without it :P
But its better with caps at both ends, see voltage regulator datasheet for details . . .