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Not sure if this will work for you, Thermal Dynamics use a Honeywell CSDA1DC on their units.
http://datasheet.octopart.com/CSDA1D...heet-18886.pdf
Al.
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current transformer to OK TO MOVE signal! (DTHC MP3000) Hi all, recently discovered that my plasma has no OK TO MOVE signal and I must add a Current Transformer to the sensor card REV12,
I have seen some providers in my country who may have CT same or similar to that offered from candcnc,
the question is! the CT of candcnc have any special feature that can not be replaced by another one for 35 to 200A
if so, what would be the value of the Power Resistor across terminals?
thank a lot!
Not sure if this will work for you, Thermal Dynamics use a Honeywell CSDA1DC on their units.
http://datasheet.octopart.com/CSDA1D...heet-18886.pdf
Al.
CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
thanks a lot What a coincidence! I have a thermaldynamics cutmaster151, but I'm outside the U.S., and here at least, I could buy a TC as offered candcnc, just that I'm doubtful if the TC from candcnc has some special features, because I have the dthc - MP3000!Originally Posted by Al_The_Man
anyway thank you very much, you are very attentive!
A current transformer is a very simple device. It is two coils of wire on a common magnetic structure and insulated from each other. It works based on a common law of magnetics that states AC current flowing in one winding is reflected as a current flowing in the other winding at a ratio of the windings to each other. With a CT the primary is the conductor that carries the high current. The number of times it passes through the center of the transformer is it's turns count. Some CT's have the primary wrapped on the structure and the currrent is inserted in series with the primary current path. Typically because of wire sizes and other constraints High current versions just have a round magnetic structure and the primary conductor is passed through the center and the secondary is wound around the core. The ratings are expressed as tha ratio of currents so a 200:5 ratio says if you pass 200 amps of AC through the Primary wire (one full wrap) you Can get 5 Amps of current in the secondary. Conversely if you pass 100A you get 2.5 Amps and so forth. Since the secondary current has no load you have no voltage (which is easier to measure than current). The secondary resistor (across the secondary) forms the "Load" and develops a voltage using good old OHMS Law. It states that E = I X R were E = volts, I = Current and R = resistance. If we know any two of the values we can solve for the third. So we have a current transformer that can develop say 1A secondary at 50amps primary . If we put a 10 ohm resistor as the load the equation says we will read a 10 volt potential across the resistor.
The circuit on the rev12 card is designed to operate from about 4VAC (using the on-board doubler) to over 20VAC. By adjusting any of the factors you change the equation. A wire passing through the center but not making a complete wrap is counted as 1/2 turn. That means the amount of current in the secondary is now half of the full turn and if you put two complete turns it's double the single turn. If the resistor remains the same the voltage would be in direct proportion to the ratio change, Adding one more warp increases the voltage in porportion (2 times in this case).
For the THC SENSOR Card with the MP3000, The AC voltage is rectified on the card and an adjustable trip circuit is used to power a small relay that closes isolated contacts back to the port pin for ARC OK. The CT must be able to take the full max current expected and not saturate. Like all magnetic structures there are other factors and the frequency response is dependant on the material used (usually high permeability iron or ferrite) and for most high current CT's used to sense 50 to 1000 Amps, the frequency range is about 40 to 400 hZ.
Sensing DC current is another story since the laws of mutual inductance don't work. Just as you can't "transform" DC through magnetics you can't sense DC current through simple windings through mutual inductance. While you can sense the change in the magnetic field intensity with changing current in a wire or magnetic structure it requires sophisticated devices or something inserted in the pirmary current path and is not self powered like the AC CT.
There are several listings on EBay for low cost cuttent transformers of the type you can use. The value of the resistor should be such that at the lowest current you will be using, there will be at least 5Volts AC across the resistor. It must be below 25VAC at the highest current. A 5:200 like we sell and a 15 ohm 10W resistor will work with most plasma cutters from 35A to 100A models. Ours comes with the resistor. As long as the ratios work out and you apply the right number of primary wraps and the right resistor across the secondary, just about any single coil current transformer will work with ratings for yous max current like these on Ebay 150374999354.
TOM Caudle
www.CandCNC.com
Hello all,
I have just installed my CT or "Hawk Eye" on my TD this past two days ago. The current transformer is a very simple device and im sure any type would work as long as it is in the parimeters of toms #s. As for he developed the rev 12 card (and all others)and knows how it works best. I just recently talked to him about this issue couple days ago. I believe I am running the 35 to 100amp CT from candcnc, if you went to a 30 to 200amp in my theory the accuracy on the #s wouldnt be as good because it covers a larger amp range. But thats my opinion I would stick with what he says. and for the resistor I picked one up today, 15ohm 10 watt sand compressed which should work fine. I also removed a red crossover plug/pin to help give me a higher CT # for more accurate #s going out to the cp and mp 3000....
TY dustin407, can you show me where to attache this ct? do you have any wiring diagram of the thermaldynamics and the Current Transformer?
in the specification of the CT make reference about a 30x10mm rod and 21mm cable and this make me doub a lot!
apologize for my ignorance, this is my first activity with one CT,rather, I've never held one of these with my hands!
Carl,TY dustin407, can you show me where to attache this ct? do you have any wiring diagram of the thermaldynamics and the Current Transformer?
in the specification of the CT make reference about a 30x10mm rod and 21mm cable and this make me doub a lot!
apologize for my ignorance, this is my first activity with one CT,rather, I've never held one of these with my hands!
Did you give Thermaldynamics automation group a call? I was having issues with the CT and RF noise. TD told me how & where to tap into the main board on my Cutmaster 52 to get a OK to move signal. I got rid of the CT and all is fine. BTW I still have the CT. PM me if you might be interested in it
Mike
Mike, I talked to customer support from TD for hours about the ok to move signal. They thought I was talking a different language...lol They never did give me an answer if my unit had on or not. So I installed the CT anyway to stop the bull****. I have the cutmaster 81 if you Know , somewhere I can tie in at...??
Carlos, the CT is basically a plastic donut, about 4" s in Diameter. You just slip one of your hot wires(going into the plasma) threw the donut and plug it back to the terminal block the hot(prob. a black wire) was originally at. I do have a CT diagram if you want I can send it to you.
Here is the TD automation people I talked to (1) 888-832-3477 . They knew exactly what I was talking about. It could be that the 51, 81, 101 etc series does not have the same hookup as the 52, 82, 102, etc. I have a 52 series and it has a 8 pin plug to get the basic automation signals. It was $35.00 for the wire hareness, I get, OK to move, torch on -off and torch volts out of it. I hooked up the appropriate wires to the controller plug end and it worked great.
Dustin, please send it to me Xp carlosescuela@hotmail.com or krlosescuela@yahoo.es, I like being able to identify that hot wire, thank a lot dustin!
Mike: The older versions you listed do not have an easy to interface to source of the signals. You had to buy their $$$$ CNC interface card (of which only the OK TO MOVE signal was usable). TD finally woke up and realized that Hypertherm has had easy to interface to on their 1000 line for years. The smaller units (600 and 900) don't have the connections and still need the CT. I don't know why it took TD so long to make it easy to interface to their machines to do CNC. It cost them in sales.
TOM Caudle
www.CandCNC.com
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