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by siqu
Fri May 17, 2013 10:05 pm
Forum: General discussion
Topic: What would you use ??
Replies: 4
Views: 1215

Re: What would you use ??

Hi, siqu. A current meter has to offer a very low resistance to the rest of the system, and the low resistance shunt connection is traditional, cheap and effective. The small voltage drop across the shunt resistor, which could be a massive bar of metal ( for large currents) provides a linear signal...
by siqu
Fri May 17, 2013 8:11 pm
Forum: General discussion
Topic: What would you use ??
Replies: 4
Views: 1215

Re: What would you use ??

Hi and thanks for reply.

Is it the only reason to use a shunt resistor and not hall effect sensor.
by siqu
Fri May 17, 2013 4:24 pm
Forum: General discussion
Topic: What would you use ??
Replies: 4
Views: 1215

What would you use ??

Hi all.

Im thinking, why all current meters use shunt resistor and not hall effekt sensor ?
By the way, that is the difference.

If you should build a current meter that can measure up to 1 A dc, what would you use ?

Thanks
by siqu
Fri May 10, 2013 2:44 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

Hi,

It works perfekt now. Thank you so mutch for your time, i dont hope it was wasted ..

Without you i wouldnt be able to manage this.

Thanks again!
May good bless you . ;)
by siqu
Thu May 09, 2013 10:09 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

Do i need to put this to my code ADC bits * ( 5 / 1023 ) ?
When you write adc bits do you then mean 10 bits cuz that is my adc.

and when i type it in python i don get any result.

please se my code, second last line, and help me. :oops:
by siqu
Thu May 09, 2013 9:45 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

Do i need to put this to my code ADC bits * ( 5 / 1023 ) ? YES Can you write the line of code for me, cuz when i do it i dont get any result at all. Only reading of 0 V no mather what. You really have know some stuff here. Thank you so mutch. I have been dealing with ADCs at low speed to higher tha...
by siqu
Thu May 09, 2013 9:36 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

1) Why do i need a 186K from pin 4 to GND when i have it from output to pin3 ( R4) If you dont you do not have a BALANCED differential amplifier configuration look up opamp differential amplifier. and by the way those resistors better be 1% tolerance or better. Okay i will read more about the diff ...
by siqu
Thu May 09, 2013 8:09 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

By the way, the adc dosnt care if i have put unused cnannels to GND or not.. But if i write approx 4450 / 1024 in my code instead of 3909/ 1024 then i get almost perfect in all positions .. Why ? Because your calculation is WRONG... The ADC converts analog voltages between 0 and 5V to ADC count val...
by siqu
Thu May 09, 2013 8:03 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

1/ you are missing a 186k resistor from op-amp pin 4 to gnd THAT will improve stability and accuracy. 2/ for 3.9V out of op-amp approx 21mV in which is approx 1A, BUT what voltage is the current terminals sitting at with respect to op-amp gnd? 3/ If doing low speed sampling (<100Hz) then I would pu...
by siqu
Thu May 09, 2013 7:04 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

By the way, the adc dosnt care if i have put unused cnannels to GND or not..

But if i write approx 4450 / 1024 in my code instead of 3909/ 1024 then i get almost perfect in all positions .. Why ?
by siqu
Thu May 09, 2013 7:00 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

Yes ADC reference voltage must be the same or higher than maximum analog input. ADC digital supply is usually different pin. Without seeing your circuit, what signal source is and knowing what the ADC is cant be much more help. For example are unused analog inputs grounded? What is the op-amp circu...
by siqu
Thu May 09, 2013 2:21 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

Usefull info .. Better than our teacher .. thx. Then i understand it clearly. I have another issue with my adc. The analog signal to adc is 3.9V, i supply the adc with 5V but my measurements is not accurate at high voltage .. But, if i supply it with 3v3 then it is accurate at high voltage input but...
by siqu
Thu May 09, 2013 12:52 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

No. The two numbers are not related to each other. You get two samples per second. "10 bits" only tells you how accurate those two samples are. If you want more samples per second, all you have to do is to reduce that "0.5". I don't know what you can reduce it to, because I don't know what ADC you ...
by siqu
Wed May 08, 2013 10:43 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

rurwin wrote:You have two samples per second (2Hz), each of which is accurate to one part in 1024 (10 bits).

Hi again,
So as i understood, i have 1024 parts = 10 bits right ? 1024*2Hz = 2408Hz
by siqu
Wed May 08, 2013 6:41 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

Because 0.5 is the period and the reciprocal of period is frequency, hence 2 Hz. Frequency = 1/period Aha, offcurse. so my adc reads the analog input every 0.5 sec right ? So it means that , the speed of my adc is 2hz, and that is how fast the adc is reading the analog input witch is in my output o...
by siqu
Wed May 08, 2013 6:11 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

Re: HELP! Sampling frequency

Hi, and thanks for fast reply :o

I want to ask you how did you calculate 0.5 to be 2 Hz,

I used a eksample form arudinio, im not god at coding self. :(
by siqu
Wed May 08, 2013 4:59 pm
Forum: Other projects
Topic: RS323 to pi ?
Replies: 15
Views: 3827

Re: RS323 to pi ?

Dam good info :D Another question is : How do i found out what my sample frequency is on my circuit ? http://i48.tinypic.com/10h5zt0.jpg What has this picture to do with anything? At first glance it looks like a current detector with a differential amplifier http://en.wikipedia.org/wiki/Differentia...
by siqu
Wed May 08, 2013 4:57 pm
Forum: Other projects
Topic: RS323 to pi ?
Replies: 15
Views: 3827

Re: RS323 to pi ?

You can get a very good approximation (depending on how well the circuit is made and device variances) of the circuit bandwidth as it does not have a sampling frequency as it is a straight forward differential op-amp configuration, not any form of ADC. Get the Unity Gain Bandwidth figure from the d...
by siqu
Wed May 08, 2013 4:47 pm
Forum: General discussion
Topic: HELP! Sampling frequency
Replies: 24
Views: 3263

HELP! Sampling frequency

Hi all. I have a question about sampling frequency. What is the sampling frequency using this example , and explain how you found the result. The ADC is mcp3008 the same as in the project bellow. Im using the same code but for another project. Current meter. The example is taken from : http://learn....
by siqu
Mon Apr 15, 2013 10:10 pm
Forum: Other projects
Topic: RS323 to pi ?
Replies: 15
Views: 3827

Re: RS323 to pi ?

Dam good info :D

Another question is :

How do i found out what my sample frequency is on my circuit ?

Image
by siqu
Sun Apr 14, 2013 8:08 pm
Forum: Other projects
Topic: RS323 to pi ?
Replies: 15
Views: 3827

Re: RS323 to pi ?

Im not sure that you understood my quiestion. Im talkin about convert RS232 signal to usb signal so it can be used to pc that dont have RS232 . Cuz, my dont have RS232 only usb, VGA HDMI etc.

Tjek picture and the red ring :oops:

Image
by siqu
Fri Apr 12, 2013 10:26 pm
Forum: Other projects
Topic: RS323 to pi ?
Replies: 15
Views: 3827

Re: RS323 to pi ?

aha, thx alot.

Another fast question: is it possible to have a rs232 converter to usb and it will still work as if i directly connected the rs232 directly to the pc.. Hope u understod my question. Im from Danmark so my spelling isnt prety. :roll:
by siqu
Thu Apr 11, 2013 4:06 pm
Forum: Other projects
Topic: RS323 to pi ?
Replies: 15
Views: 3827

Re: RS323 to pi ?

Thanks for you reply.

So you recomend me to use MAX3232 .

I found this projekt with the MAX323
http://poli.cs.vsb.cz/misc/rasp-pi-sp/

I just need to copy this and it will work right ?

Again, thanks.
by siqu
Thu Apr 11, 2013 3:38 pm
Forum: Other projects
Topic: RS323 to pi ?
Replies: 15
Views: 3827

Re: RS323 to pi ?

I have som data going into the pi, and i wont that data to be trasferd to a pc trough a RS232 interface. That data need to be shown in a pc terminal. I found this projek, take a look. http://homepage.eircom.net/~nigelbrooke/Electronics_Projects/RS232_pi_Adapter_Board.html But my problem is that i ca...
by siqu
Thu Apr 11, 2013 2:58 pm
Forum: Other projects
Topic: RS323 to pi ?
Replies: 15
Views: 3827

RS323 to pi ?

Hi all, I m building a currentmeter and the data im getting from the adc need to be showen on a pc terminal. I made it work fine with the PuTTy terminal but the point is that it schould work with RS323 and the data need to be shown on a pc terminal like ( hyper terminal win xp or so ) Any projekts s...

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