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Gonzakpo
Joined: 28 Aug 2006
Posts: 43
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 30 Aug 2006 19:55 Re: Digital oscilloscope Project |
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Hello
Does anybody know an operacional capable of allowing higher tensions in the input than the power suply ones?
My idea is the next one: I want to develope an eficient protection for my adc. The idea is to power the operational between the adc conversion limits so if a higher tension input is received, this tension will be cut between the suply limits in the output of the operacional protecting the adc.
And also it's an useful idea because I can visualize instantly from the oscilloscope screen that something is wrong in the input signal (it is cut).
If anybody knows a similar way for protecting the adc please tell me!....
(I want some protection that doesn't stop the oscilloscope operation)
Thanks!
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Nimer
Joined: 26 Apr 2005
Posts: 216
Helped: 25
Location: PALISTINE
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| 30 Aug 2006 22:05 Re: Digital oscilloscope Project |
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hi
didnt understandyour idea well...elaborate more
regards
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Gonzakpo
Joined: 28 Aug 2006
Posts: 43
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| 30 Aug 2006 22:51 Re: Digital oscilloscope Project |
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It's simple,
The idea is to suply an operational amplifier (OP) between the adc input maximun voltage ranges....
For example between +0.5V and -0.5V.... (maximun input voltage range of my adc is 1Vpp)
Also, configure the GAIN of the OP to 1. (A=R2/21)
And finally, (and this is the feature I'm looking for).... This OP MUST allow higher voltages (in the input) than the suply onces (-0.5V / +0.5V).....
For example 30V!!!
The purpose of this idea is to "cut" the part of the signal wich exceeds the input maximun voltage ranges.
I'll will upload aa example drawing for you. The problem is that I don't know how this process is called in english.
Remember, the OP I'm looking for MUST allow higher voltages (in the input) than the suply onces!.
Thanks!.
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Ave_Rapina
Joined: 06 Jan 2004
Posts: 100
Helped: 13
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| 30 Aug 2006 22:59 Re: Digital oscilloscope Project |
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Hello
why not use an simple zenner with the tensio you want to protect
for exemplo maximum is 5V you can put an 5.5v zener with an lower resistence a limit the input tension
if yo need for + and - tension just use 2 in serial in reverse one of the other.
This increase a little bit the limit tension but if you use an 5V zener the limit tensio is 5V +0.7V from the other zenner
The reverse is equal
Regards
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Gonzakpo
Joined: 28 Aug 2006
Posts: 43
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| 31 Aug 2006 3:15 Re: Digital oscilloscope Project |
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Yes, it's a posible solution, but I don't know why, I don't trust in zeners
It's a very expensive design to trust in a simple zener,
Anyway, I'll keep that solution in mind. Probably I'll end up doing that.
Thanks.
Any more ideas?
EDIT: I've just figure out something. My Adc limits are +0.5V to -0.5V so a zener or a diode aren't useful in this case because the adc limits are lower than any zener or diode "triger voltage"... :S
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jackson1985
Joined: 09 Sep 2006
Posts: 1
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| 09 Sep 2006 12:26 Re: Digital oscilloscope Project |
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| hi guys can ny1 help me in guiding me a good project (final year) related to my subject i.e electronics n instrumentation...
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melc
Joined: 08 Apr 2005
Posts: 390
Helped: 45
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Giuss
Joined: 16 Oct 2006
Posts: 37
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| 16 Oct 2006 21:20 Re: Digital oscilloscope Project |
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I'm working to an homemade DSO too and my prototipe is working but needs improvents
This is a short summary of my project :
ADC TLC5540
CPLD Xilinx XC9572
RAM Cypress CY7C199
CPU PIC16F877
30 Mhz clock
Now I'm working to improve it :
Going to 40 Mhz clock
Add a digital trigger
Add an USB connection
More to come...
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funghome
Joined: 15 Oct 2006
Posts: 7
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| 22 Oct 2006 10:21 Digital oscilloscope Project |
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i am interesting to this project.
http://www.cmccord.co.uk/FYP/index.htm
but while file is final hex file in
http://www.cmccord.co.uk/FYP/DownLoad/PicCode.zip
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CMOS
Joined: 06 Jan 2004
Posts: 672
Helped: 26
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| 22 Oct 2006 10:38 Re: Digital oscilloscope Project |
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| funghome wrote: |
i am interesting to this project.
h**p://www.cmccord.co.uk/FYP/index.htm
but while file is final hex file in
h**p://www.cmccord.co.uk/FYP/DownLoad/PicCode.zip |
It is a very low frequency scope (5KHz) and practically of no use!!
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nsakan
Joined: 16 Aug 2006
Posts: 22
Helped: 1
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| 23 Oct 2006 17:17 Re: Digital oscilloscope Project - concerning higher voltage |
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Gonzakpo asked a question about having higher voltages than maximum ADC input
> The idea is to suply an operational amplifier (OP) between the adc input maximun
> voltage ranges....
> For example between +0.5V and -0.5V.... (maximun input voltage range of my adc is > 1Vpp)
> Also, configure the GAIN of the OP to 1. (A=R2/21)
Please look at the atached png figure area A abd B between 2 and 3
You coud see an easy solution for Your problem, use two clamping diodes, they must be atached to the supply pins of the devices that You have to protect. Also it could be advisable to have some resistance beween X1-1 and diodes, jut in case that ne overvoltage is not spike but constant signal, like in Your case.. Lot of modern opamps have protection diodes inside of them, please reas the datasheet of both opamp that You would like to use and AD converter carefuly. Also be careful not to slow down the AD convereter input with the slow opama. When You are looking for the opama characteristics, note the the bigest frequency at which Your opamp is capable to delivet 1Vpp swing (for exmple the lrgest frequency tht You coud cheeve with OP07 is something between 60kHz - 80kHz, pg. 7 of OP07C Analog evices datasheet fig. TPC17). It is most likely thay Your ADC have the protection diodes inside of it, and the simplest solution is just to add some resistance in front of it. With such meho You cou hve higher voltages than opamap +/- supply voltage applied, the higher voltages would be cutt-off. Try to make some auxulary supply with nice capacitance, not only big but with low ESR and combination og several types of capacitors for Your cllamp diodes that would keep them on +0.5V and -0.5V, but first carefly reed ADC datasheet and find some aplication notes for it.
I might have some time on weekend, so if You would like send me more details about ADC and I will try to tell You something more.
Sincerely Yours,
Nenad Sakan
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miki.krejci
Joined: 20 Nov 2006
Posts: 1
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| 22 Nov 2006 9:53 Re: Digital oscilloscope Project |
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Hallo everybody,
I want to made USB oscilloscope with using FT2232C. Sampling rate about 1Mhz. I want use 12-bit A/D converter. Have you somewhere seen some scheme with input circuits? I do not know how do to range changed automaticly or how can I control range with using two bits.
Thanks for help!
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alphi
Joined: 23 Dec 2001
Posts: 439
Helped: 1
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| 25 Nov 2006 7:36 How can I do with low sample rate with TLC5540? |
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I use TLC5540 for my home DSO,but TLC5540' min sample rate is 5MHZ.So if i need low sample rate(example 100KHZ),how can I do with it.
my systerm:TLC5540+XC9572+MCU
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dainis
Joined: 15 May 2001
Posts: 1453
Helped: 56
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| 25 Nov 2006 9:39 Re: How can I do with low sample rate with TLC5540? |
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| alphi wrote: |
I use TLC5540 for my home DSO,but TLC5540' min sample rate is 5MHZ.So if i need low sample rate(example 100KHZ),how can I do with it.
my systerm:TLC5540+XC9572+MCU |
Skip some samples, sampling on 5MHz and use each 50 sample ?
Or use signal averaging by software ?
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alphi
Joined: 23 Dec 2001
Posts: 439
Helped: 1
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| 25 Nov 2006 14:35 Re: Digital oscilloscope Project |
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| if I use 5HMZ for TLC5540,and use 50 sample for one data,then i can get 100KHZ sample rate.but it will make memory deepth become very small,if I have 128Kbyte sram,and i can only use 128Kbyte/50.
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computer_engineer
Joined: 12 Feb 2007
Posts: 3
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| 12 Feb 2007 9:43 Digital oscilloscope Project |
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any one can help me plz? i want to know if ubicom ip2022 accept sinesoidal signal? i need to measure voltage and current signals an calculate real power.
Added after 5 minutes:
i need ur help quickly plz. any one can help me. plz peply me quickly. my project raquire measuring voltage and current of each home and calculate apower consumpsion. i need to know does the ubicom ip2022 adc accept sinesoidal signal. if does not what is the solution???????????????? plzzzzzzzzzzzzzzzzzzzzzzz
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mayo123
Joined: 22 Sep 2005
Posts: 13
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| 12 Apr 2007 15:19 Re: Digital oscilloscope Project |
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| monnoliv wrote: |
Hi everybody,
After more than a month of rest, here is the 6th revision of the DSO (register to see the schematics):
[url]h**p://164.15.88.56/site.php[/url]
Regards, |
I try some weeks, but the site in down.
Has any a copy of this site ??
Thanks.
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rashslash
Joined: 23 Nov 2006
Posts: 28
Location: pakistan
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| 27 Apr 2007 15:10 Re: Digital oscilloscope Project |
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| well use tlc549 serial 8 bit adc from texas instruments and use the parallel port
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computer_engineer
Joined: 12 Feb 2007
Posts: 3
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| 20 May 2007 9:13 Digital oscilloscope Project |
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hi every one .... ineed ur help
i use UBICOM ip2022 as afield unit and i heve to calculate the real power consumption of a house i used 2 channels of ubicom ADC and fed voltage to one channel and the current to the other channel.. i rised the voltage and current level by arrefrence voltage becoz i don't know if UBICOM's ADC accept negative voltage or not and i multiplyed each voltage sample by current sample over aperiod and then diveded the accumlation result by the no. of samples did i use acorrect method plz help meeeeeeeeee
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adidex
Joined: 04 Jan 2005
Posts: 11
Helped: 1
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| 30 May 2007 21:26 Re: Digital oscilloscope Project |
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| CMOS wrote: |
| nikifena wrote: |
Are you sure ?
| Quote: |
| The archive contains the schematics, PCB and the byte-files needed to program the microcontroller and the cpld: eoscope_1.2.zip |
h**p://www.mindbend.ro/eoscope/download/eoscope_1.2.zip
good luck  |
Yes I am preety sure....The files are in compiled form. No source code is provided. |
Hello,
We decided to public the sources of the project in the meantime, so now enybody should be able to make changes in the code.
We have also posted some other projects on a new site, www.eosystems.ro , the old web page (that one on the mindbend.ro domain) is obsolete and will be removed soon. I hope you can find some interesting projects on the new site, unfortunately our time is very limited so the updates on the site will not be very fast, but we have some projects wainting to be published.
So .. enjoy, and please send us some photos if you build some of our projects, and maybe send us the code too in case you make some changes, so that we can publish them on the site (hmmm .. maybe a new LCD interfacing is a good idea, or a PC connection  ).
Adrian & Daniel
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CMOS
Joined: 06 Jan 2004
Posts: 672
Helped: 26
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| 31 May 2007 6:22 Re: Digital oscilloscope Project |
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| adidex wrote: |
Hello,
We decided to public the sources of the project in the meantime, so now enybody should be able to make changes in the code.
We have also posted some other projects on a new site, www.eosystems.ro , the old web page (that one on the mindbend.ro domain) is obsolete and will be removed soon. I hope you can find some interesting projects on the new site, unfortunately our time is very limited so the updates on the site will not be very fast, but we have some projects wainting to be published.
So .. enjoy, and please send us some photos if you build some of our projects, and maybe send us the code too in case you make some changes, so that we can publish them on the site (hmmm .. maybe a new LCD interfacing is a good idea, or a PC connection ).
Adrian & Daniel |
Thats great news. Thanks ! 
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bamdad
Joined: 14 Nov 2001
Posts: 116
Helped: 5
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| 15 Jun 2007 22:42 Re: Digital oscilloscope Project |
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Dear All;
Is there anyone who knows how to implement a reconstruction algorithm for equivalent time sampling? besides, all the input protection methods I see around, relies on two diodes to supply rails to protect the sampling device, this has two draw backs, in high freqs, the diode capacitance will limit the signal bandwidth (specially when the series resistor comes between the diodes and the sampler), and this is not a linear effect, since the diode capacitance varies quite much with the reverse bias voltage... another point, this protection stage changes the input impedance of the sampler when it is clipping... does anyone know a better protection mechanism for a high speed oscilloscope, say, something about 100MHz?
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pmhunt
Joined: 26 Jan 2006
Posts: 3
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| 27 Jun 2007 9:50 Re: Digital oscilloscope Project |
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| Quote: |
| try to use gameboy for small oscilloscope |
I am currently developing a circuit that uses the Gameboy advance to take samples of upto 100Msps
using a fifo and CPLD
www.cardiagnostic.co.uk/gbadso.htm
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Nick18
Joined: 03 Feb 2006
Posts: 6
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| 27 Jun 2007 15:07 Re: Digital oscilloscope Project |
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| mayo123 wrote: |
| monnoliv wrote: |
Hi everybody,
After more than a month of rest, here is the 6th revision of the DSO (register to see the schematics):
[url]h**p://164.15.88.56/site.php[/url]
Regards, |
I try some weeks, but the site in down.
Has any a copy of this site ??
Thanks. |
I'm asking the same. How about this project? Project obosolete?
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Vacuum
Joined: 26 Jun 2007
Posts: 13
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| 28 Jun 2007 15:59 Re: Digital oscilloscope Project |
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Hello dear all.
I also develope my scope. In my plans to make it more versatile:
First of all in my plans to make programmable attenuator. But is seems too difficult... So it would be wonderfull to use ready made. Whether there are suppliers of P.A. on market?
Second: protection of overvoltage.
Third: to make RIS mode. With it I can observe periodical signals of very high frequency. Is it possible realize in fpga?
Many thanks!
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miniK0bo
Joined: 16 Jul 2005
Posts: 7
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| 11 Nov 2007 13:24 Re: Digital oscilloscope Project |
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hey all,
I also was thinking about building a DSO. I came across this topic and notice the similarities. So far I've split my design in two parts. Digital part with FPGA, SDRAM and USB2 interface. Analog part with 100MHz ADC and FIFO. The digital part I finish building it (see attachments). I still need to start the analog part (/me not so good in analog). I was wondering what the status is of the design, did any build it yet?
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judasdsc
Joined: 14 Jan 2007
Posts: 7
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| 11 Nov 2007 14:24 Re: Digital oscilloscope Project |
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| seems good. Do you have web site about this project? Any schems?
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miniK0bo
Joined: 16 Jul 2005
Posts: 7
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| 11 Nov 2007 19:46 Digital oscilloscope Project |
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| sorry no website yet, I could post the schematic one of these days
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picnoobie
Joined: 19 Nov 2006
Posts: 89
Helped: 6
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| 14 Nov 2007 18:14 Re: Digital oscilloscope Project |
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| EDIT: how stupid of me, the link I posted was in the first page of this thread, I just accidentally landed on this thread during my search and didn't read up in the begining. I apologize.
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miniK0bo
Joined: 16 Jul 2005
Posts: 7
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| 22 Nov 2007 18:43 Re: Digital oscilloscope Project |
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as promised: the schematics
so far there is one mistake in the schematics. the reserved pin on the fx2 chip needs to be grounded!
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