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musti463
Joined: 19 Sep 2013 Posts: 66
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My Schematic and Your Recommendations |
Posted: Sat Sep 20, 2014 8:58 am |
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Can you tell me your recommendations about my schematic?
https://yadi.sk/i/yB38eXkXbapCH _________________ M.Emir SADE
Last edited by musti463 on Mon Sep 22, 2014 4:51 am; edited 1 time in total |
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dyeatman
Joined: 06 Sep 2003 Posts: 1924 Location: Norman, OK
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Posted: Sat Sep 20, 2014 2:06 pm |
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OK, so you show a schematic.
What do you want to know.
What is it supposed to do?
Where is your CCS code? _________________ Google and Forum Search are some of your best tools!!!! |
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temtronic
Joined: 01 Jul 2010 Posts: 9177 Location: Greensville,Ontario
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Posted: Sat Sep 20, 2014 3:10 pm |
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I could make about 40-50 'recommendations' though this is not the forum for that rather dedicated programming of PICs using CCS C.
A schematic is just one piece of the puzzle to get a product to market. You also need GREAT board layout(easy these days) as well as very good code(super easy with CCS C !).
hth
jay |
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SherpaDoug
Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA
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Posted: Sat Sep 20, 2014 7:22 pm |
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Hard to say much without knowing a lot about the application, but be careful how you lay out your grounds. _________________ The search for better is endless. Instead simply find very good and get the job done. |
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musti463
Joined: 19 Sep 2013 Posts: 66
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Posted: Sun Sep 21, 2014 6:31 am |
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Yes, i know there is no ccs code. But i wanna create firstly hardware correctly and later create a ccs code. I want your help for my circuit schematic, later i share my layout and lastly my ccs code.
This circuit will suitable. So there are many inputs i know. There are totally 4 sensor inputs but sometimes output types can change 4/0,3/1,/2/2,1/3(mA/V) etc. And my MCU generates some values and send to operator panel circuit and display this values on GLCD. And so while values at critical. System control the crane movements with relays outputs. _________________ M.Emir SADE |
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asmboy
Joined: 20 Nov 2007 Posts: 2128 Location: albany ny
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Posted: Sun Sep 21, 2014 9:35 am |
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Differential inputs for single ended sources are delusional and a waste of parts.
this will NOT fix offsets and NOT reject common mode
( as its all common mode when unbalanced !!) BUT
WILL increase the noise floor up to 3db
in the output signal for U1 -
you would be better off with a simple
BUFFER with ONLY the 100 ohm input "bias/load/terminator left .
just tie the inverting input to the op amp output and buffer
better yet get rid of U1A as you already have a 100 ohm term resistor into the SK filter stage that follows
this design does not need U1A at all so long as there is that 100 ohm resistor present!!
a quick look says the SK follower may be only conditionally stable too !!!
you need some analog chops - don't just cut and paste circuit elements!!!
thats my advice
![Question](images/smiles/icon_question.gif) |
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musti463
Joined: 19 Sep 2013 Posts: 66
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Posted: Sun Sep 21, 2014 11:59 am |
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thank you asmboy. You mean "remove all U1:A,U2:A,U3:A.... circuits" ?. To be honest i get this circuit from an industrial device ![Smile](images/smiles/icon_smile.gif) _________________ M.Emir SADE |
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asmboy
Joined: 20 Nov 2007 Posts: 2128 Location: albany ny
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Posted: Mon Sep 22, 2014 4:23 am |
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YUP!!
just keep the 100 ohm resistor |
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temtronic
Joined: 01 Jul 2010 Posts: 9177 Location: Greensville,Ontario
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Posted: Mon Sep 22, 2014 5:12 am |
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I'd put LEDs in both sides of the opto-couplers of the 'relay outputs'. I've done this for 2 decades in my SSRs and it's saved a LOT of 2Am calls for 'no heat' ! A simple look at the board shows IF the LED is on the relay is working, so 'no heat ' problem is NOT my board must be your furnace.
As for PCB layout, bigger is better. I'd use a 4" x 6" (my standard) PCB, with fat traces for power and grounds. I prefer a checkerboard ground plane not a 'fill', especially if the 2 board surfaces greatly differ in copper. More on one side will 'cup' the PCB. Always use sockets for PIC, never run traces between adjoining pins if possible.
Why socket the PIC? 3 days after the PCB is done, you'll need more RAM, or EEPROM or the new PIC will be 1/2 the cost !
hth
jay |
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gpsmikey
Joined: 16 Nov 2010 Posts: 588 Location: Kirkland, WA
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Posted: Mon Sep 22, 2014 1:34 pm |
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While I agree with the idea of a socket for the PIC, you need to consider if it is going to be used in a high humidity or vibration environment. Both of those can make a socket more trouble than it is worth.
mikey _________________ mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3 |
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ckielstra
Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands
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Posted: Mon Sep 22, 2014 4:28 pm |
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musti463 wrote: | To be honest i get this circuit from an industrial device ![Smile](images/smiles/icon_smile.gif) | That explains why many old components are used.
BC547 I used 35 years ago and LM2576 20 years ago. They are good and cheap components but more efficient alternatives do exist. So without knowing the details of your project it is hard to tell if these are the best choice.
Why is one of the 10V inputs using other op-amps?
Do you really need an external 12-bit ADC? Many PIC processors have 10-bit ADC so you can simplify your design. Getting accurate 12-bit readings is difficult as it requires great care in PCB design and a very stable power supply. Many people design 12-bit or even 16-bit ADCs with the false assumption that it'll be accurate when it has poor design and effectively 8 to 9 bits accuracy. |
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dyeatman
Joined: 06 Sep 2003 Posts: 1924 Location: Norman, OK
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Posted: Mon Sep 22, 2014 4:55 pm |
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Isn't redesigning a commercial circuit just a bit far afield for this board? _________________ Google and Forum Search are some of your best tools!!!! |
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PCM programmer
Joined: 06 Sep 2003 Posts: 21708
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temtronic
Joined: 01 Jul 2010 Posts: 9177 Location: Greensville,Ontario
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Posted: Mon Sep 22, 2014 6:09 pm |
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ck is right about using a different PIC with a better ADC built in.It allows for as good(if not better performance),cheaper overall, easier to code,etc.
As for sockets, I've used gold plated ones and a dab of low tack sealant in industrial boards(in foundries,paint shops,etc.) for ,ugh, 2 decades(originally 16C84s) and have never had any problems related to socket-itis.
jay |
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musti463
Joined: 19 Sep 2013 Posts: 66
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Posted: Tue Sep 23, 2014 4:41 am |
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thanks for your advices. There is easy to use MCP3208 with PIC. Because there is MCP3208.c in CCS C Library right?
1-So how is 18F46K80 (internal 12bit ADC). And so there isn't AVSS pin on 18F46K80. How can i provide the good ADC performance?
2-Can ADC performance be different PIC to PIC ?
@PCM Programmer i asked same question at edaboard.com. But i found better answers and better attention here! _________________ M.Emir SADE
Last edited by musti463 on Tue Sep 23, 2014 7:29 am; edited 2 times in total |
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