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Topic: TT 100-SD  (Read 797 times) previous topic - next topic

gerko13

Hey guys,

I plan on building a current sensor with a TT 100-SD.

I tried to follow this tutorial https://learn.openenergymonitor.org/electricity-monitoring/ct-sensors/how-to-build-an-arduino-energy-monitor-measuring-current-only

But the EmonLib isn't really compatible with my TT 100-SD and the datasheet for my ct sensor isn't rich.

Any idea on how to build this ?

best regards,

Wawa

But the EmonLib isn't really compatible with my TT 100-SD and the datasheet for my ct sensor isn't rich.
What makes you say that.
The TT100-SD looks like any other current transformer with external burden resistor.
Just what the article describes.
Leo..

gerko13

When I actually tried, all the results i've got where off the charts as I was using an amps clamp to couter-check the values. I could change the 111.1 setting but there's no info on the turns, so I can't make a good calculation.

Wawa

#3
Apr 25, 2020, 01:29 pm Last Edit: Apr 26, 2020, 10:02 am by Wawa
When I actually tried, all the results i've got where off the charts...
What was the value of the burden resistor.

I calculate about 53 ohm for a peak/peak voltage of 5volt (5volt Arduino) with this 100A/33.3mA CT.
33 ohm is recommended in the article, which is a good start.
Leo..

raschemmel

#4
Apr 26, 2020, 07:05 am Last Edit: Apr 26, 2020, 07:14 am by raschemmel
Option-A:


Quote
EO=IP∗RBTR  where EO is the output voltage, IP is the current that will produce the voltage you want, TR is the transformer's turns-ratio, and RB is the burden resistance, in ohms.
datasheet

Option-B:

Wouldn't the voltage across the burden resistor be 0.033A * 33 Ohms (1.089V) rms for IIN = 100A ?
 




JCA34F

Yes, and using the 1.1V internal AREF would yield an ADC result of about 1012.

Wawa

#6
Apr 26, 2020, 09:59 am Last Edit: Apr 26, 2020, 10:01 am by Wawa
Yes, and using the 1.1V internal AREF would yield an ADC result of about 1012.
No, this is AC, not DC.

Wouldn't the voltage across the burden resistor be 0.033A * 33 Ohms (1.089V) rms for IIN = 100A ?
Yes, which is ~3volt peak/peak for the 5volt pin, or 3/5 of the range of the A/D.
Working backwards gives you a burden resistor of about 53ohms for 100A>5volt peak/peak.
Leo..

raschemmel

#7
Apr 26, 2020, 02:33 pm Last Edit: Apr 26, 2020, 02:35 pm by raschemmel
Quote
Yes, which is ~3volt peak/peak for the 5volt pin, or 3/5 of the range of the A/D.
Working backwards gives you a burden resistor of about 53ohms for 100A>5volt peak/peak.
By "working backward" you mean :

Let VP-P = 5V

   Irms = 0.033 A (33mA) (@100A)

    VPeak = VP-P /2

                            =  2.5V Peak

      Vrms = VPeak /1.41421 (SQRT(2))

                             = 2.5V/1.41421

                             = 1.7677 Vrms

      RBurden =  Vrms/Irms

                                 =  1.7677/0.033A

                                 = 53.5 Ohms

     RBurden = 51 Ohms (Nearest Standard Value)

     ?                      

JCA34F

No, this is AC, not DC.
Yes, which is ~3volt peak/peak for the 5volt pin, or 3/5 of the range of the A/D.
Working backwards gives you a burden resistor of about 53ohms for 100A>5volt peak/peak.
Leo..
OOPS, ignore me!   :-[

gerko13

thank you guys for all the answers.

https://learn.openenergymonitor.org/electricity-monitoring/ctac/ct-and-ac-power-adaptor-installation-and-calibration-theory

So following this, and your responses, instead of ""current constant = (100 ÷ 0.050) ÷ 18 = 111.11"" 111.11

I should use : current constant = (100 ÷ 0.050) ÷ 53.5 = 37,383 // 51 = 39,215 ?

Thanks !

raschemmel

#10
Apr 27, 2020, 09:41 pm Last Edit: Apr 27, 2020, 09:49 pm by raschemmel
Quote
So following this, and your responses, instead of ""current constant = (100 ÷ 0.050) ÷ 18 = 111.11"" 111.11

I should use : current constant = (100 ÷ 0.050) ÷ 53.5 = 37,383 // 51 = 39,215 ?
This response is really meaningless without defining any of your terms.
You have made no effort to define what any of those numbers represent.
We can recognize the 100 to be 100A (measured by the CT, also called IIN
We can recognize the 53.5 as the calculated burden resistor (from Wawa and my calculations)
We can also recognize the 51 to be the closest standard resistor value for the burden resistor.

I have no idea what this is supposed to represent:
Quote
current constant = (100 ÷ 0.050) ÷ 53.5 = 37,383 // 51 = 39,215 ?
It is standard practice to present you formula first (with NO VALUES)
and THEN present your solution, in the format (shown in MY calculations)

FORMULA
BLAH +BLAH = BLAH

EXAMPLE

Let Blah-A = blah
  Blah-B = blah blah
  Blah-C = blah blah blah

Then,
  BLAH +BLAH = BLAH (with values)

This part is particularly confusing:

constant current = 39,215

What is 'constant current ?'
and
if current is represented in Amps (A)

WHAT is 39,215 ?

Is that 39,215 A ? (I hope not)
Is that 39,215 mA ? (if so , WHERE ARE THE UNITS ?! ("mA")
Is that 39,215 V (I hope not)

If it is not Amps, and it is not volts , then if it is ohms, WHERE ARE THE UNITS ?! ("Ohms")

gerko13

Sorry Raschemmel, it was all written here https://learn.openenergymonitor.org/electricity-monitoring/ctac/ct-and-ac-power-adaptor-installation-and-calibration-theory

I didn't want to copy paste something too long.


current constant = (primary current ÷ secondary current) ÷ burden = x

current constant = (100 ÷ 0.033) ÷ 51 = 59,417

59,417 being the calibration in my code with the Emonlib library :)

Wawa

Just use a 100A resistive load, and use a calibration factor that displays 100.0Amp.
I assume you have a 100Amp resistive load. Why else would you buy a 100A sensor.

You could thread both wires of the AC load through the core (in opposite directions !) for 50A max.
Leo..

raschemmel

#13
Apr 27, 2020, 11:49 pm Last Edit: Apr 28, 2020, 12:28 am by raschemmel
Quote
current constant = (primary current ÷ secondary current) ÷ burden = x

current constant = (100 ÷ 0.033) ÷ 51 = 59,417

59,417 being the calibration in my code with the Emonlib library
Keep in mind that your posts are not meant only for the members who have previously responded to your
post. They are also (since this is an OPEN SOURCE FORUM) meant for all the Newbies all over the world
who are trying to learn by reading posts, whether they have a specific need for the information or not.
There are many new members who don't have a clue where to start, never having been exposed to
electronics before and responses like your previous one who leave them totally baffled.
Even I was unable to find that formula on that link.
It may be buried in one of the links on that page but all I found was this:




constant current or current constant ?

as in const current


Quote
According to Integrated Publishing: Electrical Engineering Training Series, you would use the following formula to determine average current:

 I avg = 0.636 X I max.

 I avg is the average current from zero to peak and back to zero (one alteration)

 I max is the "peak" current. (The unit of measurement for current is the ampere or amp.)

Let Irms = 100A
Then IPeak = (SQRT(2) * IRMS
                               = 1.41421 * 100
                               =  141.421 A

I avg = 0.636 X I max.
       = 0.636 *141.421 A
.      = 89.94 A

So unless you can link the page from that website that contains the formula you posted, which
is it ?

A. constant current (ie constant current circuit)
B. current constant (ie a software constant "const" reprepresenting current)
C. AVERAGE current (as explained above but self explanatory)

    Write, on a piece of paper, the formula for finding average current: I avg = 0.636 X I max.
If the answer is "B", my choice would have been "const Calibration" (calibration constant)

Also, you must not be in the USA because you have a comma instead of a decimal point, which
for us in the USA would make a huge difference.
I did the math and got 59.41, and then realized you were in some other country.

As a matter of consistency, I recommend using decimal points , because then there can be no
ambiguity. It may be correct in your country but this is an international forum and it might avoid
confusion.

gerko13

I understand, sorry for being evasive. Let me be more clear/precise.

My goal is to achieve a Blynk server [with node-red for web interface], I am going to use arduino [WeMos D1 mini Pro] and ct sensor on our CNC machines to detect if they are active, or not (as 0-2 amps : idle, 2-50 : working for exemple.).

I found a tutorial on https://learn.openenergymonitor.org/ about CT sensor and I tried to reproduce it with my TT 100-SD. In the datasheets I'm missing the secondary turn so I was clueless how to calculate the turn ratio with this
Quote
Isecondary = CTturnsRatio × Iprimary

CTturnsRatio = Turnsprimary / Turnssecondary
than I found on this page https://learn.openenergymonitor.org/electricity-monitoring/ctac/ct-and-ac-power-adaptor-installation-and-calibration-theory how to change the 111.11 default calibration for the EmonLib because when I was mesuring 0.11 amps with my clamp I was mesuring 0.45 with the TT 100-SD.



Maybe it was a wrong burden, or a wrong calibration (as I was using 111.11) or both !

I'll try to apply what you guys told me !

Thanks you!


Also yes, I am from France.

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