Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - Fernandz

Pages: [1]
1
Frequently Asked Questions / Re:How to scale an analog input data
« on: March 12, 2004, 08:56:15 PM »
I just posted in "Technical" about a sensor that has a 32 to 200 Deg. F range. This is what I know about scaling I hope it helps.
 We know that our ADC is 0-5volts and will send a count of 0 to 4092
So a 5 volt signal will be counted as 4092, and 0 volts will be a count of 0. Lets say our sensor outputs a signal thats proportional to temp. say .010v per'F and at 32 DegF we have an output of .32 volts.......... (.32 / .010v)=32'F and 200'F is an output, from the sensor, as 2 volts.......(2/.010v)=200'F

     |---|---|---|---|---|---|---|---|---|---|---|---|---|
     0      .32v               2v                               5v  ' ADC volts
               |                   |
     0      261              1637                            4092 ' Converter count
            [-- Our Sensor--]

In order to get the Converter count of 261 and 1637 I use the formula
     count=4092/5*ADC(voltage)

So count=4092/5*.32
     count=818*.32
     count=261

Once you have your converter counts then use the above formulas to read temps. EG.  temp=168*(ADC(n)-261)/1376+32

This is how I do it, keep in mind I'm no engineer and self taught.



2
Technical support / Re:Compatible RTD temp probes
« on: March 12, 2004, 08:14:51 PM »
Well no luck finding my notes but I got an interesting sensor in the mail the other day. I ordered an analog wall sensor that outputs a direct proportional reading in Deg F to voltage......So 75 'F = .75 volts. This sensor outputs .010v/'F ...........Hmmmm sounds like an LM34 sensor. The sensor and spec's can be viewed here. ATP1000  www.automated1.com  This sensor has an output of 32Deg F to 200DegF. I hooked it up to my T100MD 888 and found it to work flawless. The exact formula I am using is .

T=168*(ADC(n)-261)/1376+32          

or to display it on the LCD use:

setlcd 0,1, "Temp. =" + str$(168*(ADC(n)-261)/1376+32 )

of course keep in mind that the "n" in ADC(n) must be replaced with the correct Analog Input  1 to 8.          

3
Technical support / Re:Using the PLC to control a bus...
« on: March 08, 2004, 09:17:33 PM »
Well I'll give you my opinion I purchased a T100MD888 to teach myself more about PLC's. I found this PLC to be just a VERY powerful for the price. The best part for me is the Custom Function very very powerful. I plan on my PLC controlling my Air-conditioning system Via room sensors and my hot water boiler Via outdoor air reset. In short the Ladder + Basic make this a very POWERFULL PLC. Thats just my opinion

4
Technical support / Re:Compatible RTD temp probes
« on: March 08, 2004, 09:05:51 PM »
http://web.mit.edu/rec/www/workshop/lm335.html   This website provided some good info including a wiring diagram. The only thing you need is a voltage divider. I need to find my notes on this but i believe the equation to read the Analog input was......
                                     
  Temp=(ADC(1)-2236)*(500)/4096     for 12bit
 
The Analog inputs are 10 bit normalized to 12 bit ....The 10 bit formula would be........................

 Temp=(ADC(1)-559)*(500)/1024      for 10bit

The LM335 puts out 10mv/DEG. K   (273 Deg K) =( 0 Deg C) =( 2.73v )=(2236 converter count @ 12 bit)...... You may have to tinker with this but i believe this is how i did it. Keep in mind that the LM335 outputs Deg.Kelvin They also make a LM35 that outputs Deg.C @10mv. Ive yet to pick one up. Plus the 5 Volts from the PLC is perfect for these IC sensors.

5
Technical support / Re:Compatible RTD temp probes
« on: March 05, 2004, 08:14:11 PM »
Have you looked into an IC sensor. I have played around with the LM335 and had some good results.

6
Technical support / Example #8 in Part two
« on: March 02, 2003, 01:48:08 PM »
In part two example #8 the H.V.A.C application you show two formulas to convert ADC input to temp. S=ADC(5)*(300-160)/4096*160 and T=ADC(1)*(500+100)/4096-100. What is the reason for subtracting the temp range in the first formula and then adding the 160, and on the second formula adding the range and subtracting 100?
   My second question is im using a thermister (3,000Ohms @77 deg.F) connected to a simple voltage divider circuit. I would like to convert the 0 to 5 volt analog signal to a temperture ( 0 volts would be about 100 deg.f @ around 1900 Ohms and 5 volts would be about 60 deg. F @ around 4600 Ohms)

7
Technical support / Temperature Transmitters
« on: January 20, 2003, 03:58:46 PM »
I'm interested in useing the T100MD888+ in a building automation roll for H.V.A.C equipment. I'm a little green still when it comes to PLC's. I've noticed that some manufactures of building automation controls use 2 wire thermistors (NTC) connected straight to there analog inputs with no exterior signal conditioning can this be done with the T100MD888+ with its 5V analog output? If so where would i get this info.??

8
Technical support / Re: Using VB6 to interrorgate Analog inputs
« on: September 05, 2003, 05:22:21 PM »
Thanks.......I skipped over chapter 4 in the User Manual my fault. ;D Now i understand the command/response format

9
Technical support / Using VB6 to interrorgate Analog inputs
« on: September 04, 2003, 04:16:28 PM »
Is there a list of commands that can be used to return the values of the Analog inputs of the M-series PLC? I would like to use the MScomm control to link to the serial port.

10
Technical support / LM335 IC sensor
« on: October 30, 2003, 02:41:03 PM »
What would be the best way to hook up a LM335 sensor to the analog inputs of the T100MD? Also what formula would i have to use?

Pages: [1]