I made a software with Arduino and the device needs to take the EMC-EFT 2KV 100khz test. The hardware part of the test was left to me. Since I don't have a very close relationship with electronics, I don't know how to make these connections.
1-) There is no ground at the entrance of the device. The device only has neutral and line. How do I add a TVS diode here? (I have a 400V TVS diode)
2-) I also need to add common mode choke. But I don't know where and how to add it. Can you help me ?
3-) There is no filter on the SPI connection. Does adding a filter to the SPI connection work in EFT testing?
Do have the choke in hand or do you have to make one? What frequency are you interested in stopping with the choke? Seems like you connect one end pair of wires to the neutral and line and the other end wires of the choke to whatever you are protecting from the signal.
But since I don't have a ground connection, I don't know where to put this diode. How do I connect it to Neutral and Line? I have 5 diodes. How do I place these TVS diodes most effectively?
Without knowing more of your circuit and how it connects to the outside world it's difficult to suggest solutions. If this is a company product you might want to hire a consultant. A quick search suggests the test costs at least $1000 to perform. Typically at least 2 tests are performed to pass. i.e. the first try fails and the second on (hopefully) passes.
Thanks a lot JohnRob. I want to try this diode and if it fails later, the best solution would be to hire a consultant. Can I connect this diode in series to the circuit? What I mean is 1 serial bi-directional diode on the neutral line and 1 serial bi-directional diode on the line line. Does this provide protection for EFT? I opened this topic because I do not know the most correct placement of these diodes. Can you help me please ?
IF your Google still works, search for "tvs diode" and see the circuit schematic that you see. That shows the proper connection and also tells you why and how they operate.
I'm uncomfortable doing this because you don't even know or understand your circuit. I've been doing EMC design (as part of product development) all my career and EMC design is logical but very complex.
I realize you are hoping to "get lucky", but rarely is luck involved when dealing with EMC.
However:
Is your device AC powered? i.e. mains powered.
Does your device have a conductive enclosure (i.e. metal)?
What are the outputs? Where do they go? (external to the device).
Remove the ground symbol and what do you have? Exactly the schematic you have been working with. The protection is for transients occurring in two wires. Makes no difference is one happens to also be a ground or a common. How do you measure the voltage on your two wires? One to the other. The voltage spikes will not occur at the same time on both wires. That is the reason for the common mode choke you mentioned. Common mode means the same pulse occurs at identical times on both of your wires. The choke is not supposed to let them pass on to the following equipment. The choke will not stop a pule on a single wire, which is what the TVS diode attempts to do.
Probably not! YOU need to determine the reactance needed to choke the frequencies being choked and then you can look for common mode chokes that fit those parameters! The ferrite devices cannot work, as they have only ONE conductor space. Have you done any researching on common mode chokes for your mains power?
To understand EFT/B failure mechanisms, two aspects must be understood. Firstly, EFT/B is mostly a
common-mode test, with the transient pulses applied between power conductors and the ground plane.
Secondly, EFT/B can be classified as an RF-test, with frequency components up to a few hundred MHz.
From these two aspects, and the fact that the product under test must be 0.1m above the ground plane with
preferably air as separation dielectric, it is clear that EFT/B transient currents are essentially capacitive in
nature. Figure 4 illustrates the concept for positive polarity transient pulses. For negative polarity pulses, the
current direction reverses.
This means the voltage burst comes in on BOTH the line and neutral mains. Where it leaves depends on the physical layout of the circuit and the display.
The applied transient comes in on both the line and neutral, passes through the power supply, goes to the circuit and leaves through any clad on the bottom of the board to the ground plane via capacitive coupling.
To pass this test, the circuit and board design needs to be laid out with this in consideration. An add-on will not do it. That is unless you put an aluminum shield on the inside of the back of your device. It needs to be connected to somewhere near the internal powersupply.
