Timeline for Questions on interfacing circuit for an NPN input
Current License: CC BY-SA 3.0
21 events
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| Sep 2, 2017 at 19:44 | comment | added | user1245 | There is around 14.2VDC at Y1. NPN is not part of PFX but Y1 is the collector to the NPN we use. Y1 is not a 0-10V ect pulse input. | |
| Sep 2, 2017 at 19:24 | comment | added | jonk | @user134429 That's where we completely disagree! As I read the datasheet the NPN, PNP, and NAMUR boxes are external to the PXF-20. They are suggested connections should you be using when you use one of those three types of input devices, each of which are supported by the PXF-20. (But they are NOT a part of it.) | |
| Sep 2, 2017 at 19:15 | comment | added | user1245 | Alright I understand thanks for the suggestions (Y1 is written input but it is actually collector of NPN transistor hence it is powering NPN as in CE configuration) | |
| Sep 2, 2017 at 19:10 | comment | added | jonk | @user134429 I'm reading the datasheet. Y1 is an input. I don't see any reason to think your model is accurate. Perhaps you should contact the supplier of it. For now, we can both stare at the datasheet and both see different things. And I can't say I trust your interpretation, for now. So we leave this here. I appreciate your thoughts. But I simply can't yet agree with them and we are stuck on that point. However, that said it was still an interesting question and I did +1 it (and meant that.) I may actually play with these ideas sometime in the future, myself. | |
| Sep 2, 2017 at 19:06 | comment | added | user1245 | V1 is the voltage at Y1 when I measure it with a scope. But when I measured it with different resistances I calculated the output impedance of Y1 as 2k. So V1 and 2k is the model for Y1. | |
| Sep 2, 2017 at 19:03 | comment | added | jonk | @user134429 Also, you have a voltage source at V1. What is that doing there??? Look, you really need to get the models right. I built a "pseudo PXF-20" that I did NOT show you. I also built an "anemometer" model I also did not show you. Neither of what I built looks like your schematic. I think we hold short for now on the discussion until we can agree about what to simulate and how -- if that's your sole goal. I'd rather see exact testing on the actual equipment. The circuit is simple enough. But I think we are far apart on how to simulate the input and how to simulate the PXF-20, too. | |
| Sep 2, 2017 at 19:02 | comment | added | user1245 | PXF-20 has hysteresis but only 2.5 volt. Glitch is 12V or im still missing a point | |
| Sep 2, 2017 at 19:00 | comment | added | jonk | @user134429 That demonstrates nothing much! You need to include the PXF-20, which is what I tentatively assert has the hysteresis! The circuit I provided isn't supposed to do that, as I said earlier. If you assert that the PXF-20 doesn't have any hysteresis, you'll have to do more than use Spice on my circuit. Also, I didn't use that "anemometer" input as a Spice model simulator!! You need to create a MUCH MORE complex circuit to do that (which I did, but didn't show you.) In short, you need two more components to your model: the PXF-20 and the anemometer. Those are non-trivial. | |
| Sep 2, 2017 at 18:57 | comment | added | user1245 | Please see my edit2 I tried to demonstrate what I meant. See the 1-12V glitches. Thanks | |
| Sep 2, 2017 at 18:57 | comment | added | jonk | @user134429 I'll take your word that the PXF-20 (F2V?) doesn't have any hysteresis. I was just "interpreting" what I read, but I have no way of testing the idea. You have it and can test the idea. Use the \$Y_1\$ input (relative to \$Y_0\$) when performing the test, please. But if it isn't there, it isn't. And if not then, yes, it might be helpful to add hysteresis. (I did add a tiny bit of negative feedback to the circuit.) | |
| Sep 2, 2017 at 18:44 | comment | added | user1245 | Im sorry but I dont agree. I will simulate both circuits and upload the results. You will see lack of hysteresis at the beginning will cause glitch at the F2V input which cannot be eliminated. | |
| Sep 2, 2017 at 17:57 | history | edited | jonk | CC BY-SA 3.0 |
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| Sep 2, 2017 at 17:35 | comment | added | jonk | @user134429 The PFX-20 explicitly says (page 2) that "NPN: High > 7,5V and Low < 5V." This tells you that the \$Y_1\$ input already has hysteresis thresholds set at those levels. That's \$2.5\:\textrm{V}\$ of hysteresis! Which is pretty good. They are already providing all the hysteresis you need. So stop worrying about that part. Yes, their earthed zener supposedly keeps the line near earth. But it's not lightning protection in my mind. | |
| Sep 2, 2017 at 17:29 | comment | added | user1245 | With comparator circuit I can set hysteresis for noisy sinusoids like 100mV hysteresis. If this is not done at the beginning Y1 will not know that it was noise. I dont know if I could explain what in my mind. But one more question to you if you dont mind, in their datasheet for the wind sensor nrgsystems.com/assets/resources/an40C-IF3-interface.pdf I look at their suggested block diagram. The over voltage protection component's one leg is tied to "protection earth" not to the circuit's own ground. Is that really what is supposed to be Im really confused why it is like that. Thanks | |
| Sep 2, 2017 at 17:13 | history | edited | jonk | CC BY-SA 3.0 |
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| Sep 2, 2017 at 17:10 | comment | added | jonk | @user134429 The circuit can be simplified a little if you have your own power supply rail. But you'd need to make a FINAL decision about exactly how you want to arrange things. My own feeling is that you should concentrate on supplying the PFX-20 properly and just self-power the circuit itself from the 20 mA current source they provide. This isolates the two issues. And since the PFX-20 supplies the 20 mA whether you like it or not, might as well just use it. | |
| Sep 2, 2017 at 17:00 | comment | added | jonk | @user134429 My circuit doesn't have any hysteresis. Your PFX-20 has the hysteresis at the input \$Y_1\$. I think it would be wise to worry about lightning. But I'm not qualified to comment on providing good protection, either. I do know that it can be complicated, involving design elements of your structure and nearby areas ("rolling circles" design, for example) and also specific elements at the entry point into the home. This is why I said I might go with fiber optic cable at the home entry point. The resistance you measured seems reasonable, about twice the absolute minimum I estimated. | |
| Sep 2, 2017 at 11:50 | comment | added | user1245 | There will be 12V or 24V power supply anyway for PFX, so I was planning to use the same supply for my comparator circuit's power rails. Is your transistor circuit have enough hysteresis? Im a bit worried about overvoltage caused by weather lightning ect. Can I add TVS between sensor output and the circuit in your transistor circuit like in my circuit? | |
| Sep 2, 2017 at 11:45 | comment | added | user1245 | Many thanks for the nice answer. You are right Y2 is a current source I verified it by connecting 220 Ohm resistor I read around 5V. But I dont know why they write 0-20mA instead of just 20mA is its a current source(?). Also what's the purpose of Y2 as current source, I would think better to provide a voltage source for one's gadget. I opened the sensor and it is like 4 pole magnet rotating and inducing voltage across the coil. So the coil resistance hence the sensor's resistance I measured as around 680 Ohm. | |
| Sep 2, 2017 at 7:41 | history | edited | jonk | CC BY-SA 3.0 |
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| Sep 2, 2017 at 7:28 | history | answered | jonk | CC BY-SA 3.0 |