boylesg
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So these things are common mode filters right?... and any over voltage protection that clamps above say 275V AC is unlikely to be of much use at 24V but if it is employed, you can change to lower clamping voltage devices.
Brian.
The digital electronics is going to draw up to 1A perhaps. Or not much more than that.Hi,
such a filter has two functions:
* PASS signals. This is 24V AC for your connected device to operate.
--> We don´t know how much current your device draws nor what voltage drop is allowed.
* ATTENUATE signals. High frequency. We don´t know which frequency range of noise you expect (or the frequency range that you want to be suppressed). And we don´t know the HF volotage levels. Neither the expected noise level nor how much you want it to be suppressed.
***
Let´s compare the filter with a bungee rope.
* on the one hand the rope needs to be strong enough to carry your weight,
* on the other hand it needs to be elastic enough to softly decelerate the speed ... without hurting you.
So it depends on a lot of things if the bungee jump is "successful", like: Jumper´s weight, jumping height, rope length, rope elasticity, maximum rope force rating....
Klaus
As for frequency - well all the AC line filters in TVs and laptop power supplies must aim to block a similar range of frequencies likely to come in through the wall sockets.The digital electronics is going to draw up to 1A perhaps. Or not much more than that.
A 20 x 4 LCD screen, WiFi, and relay board.
Also Arduino Mega, data logger shield, HC-05 - all low current stuff.
The 24VAC solenoid valves draw approximately 250mA when on.
Wurth Electronik has a EMI filter design tool on their weksite. You may need to register first.Is there an online calculator that any of you can recommend? To give me start in this new endeavor for me.
I found this to save me the hassle of registering:Wurth Electronik has a EMI filter design tool on their weksite. You may need to register first.
I don't think the filters on that site will work as a Line Filter as they assume no load impedance so are likely to interact with your circuit. For an EMI filter you have to specify your impedance of your load, know the frequencies your trying to filter, and the type of noise otherwise the effects will be undersirable to say the least. 50Hz is the line frequency which far away from digital/switching circuitry noise. You really need to know what frequencies are generating to understand what needs filtering. Looking at your circuit the biggest source of noise will be the DC/DC conveter which will have high energy dv/dt nodes and probaby operates @ >100Khz. Noise will likely be at the switching frequency upwards so as far as filtering in concerned knowledge of this and the amound of noise its generating is mandatory for EMI. As a start if i were guessing i'd assume differential emissions will be the target for the filter you could try a filter pitched at 20db Attenuation 100khz with a 2A load as a start. Its highly like the converter is higher than this but the attenuation will be greater at higher frequencies. If any issues are common mode then this won't help.I found this to save me the hassle of registering:
electronicbase.net/low-pass-filter-calculator/
LC low pass filter calculator.
How far above 50Hz (mains AC) would you recommend going?
I don't understand Klaus. What other information specifically.what about the other information?
Klaus
I don't see how it can be anything to do with anything on my board Klaus.Hi,
You ask for a filter, but your sketch is missing the filter at all.
You ask for a filter (which is a solution), but you did not mention the problem you want to solve with the filter.
Is it for passing an EMV test? Or do you want to solve a malfunction problem? Something else?
I asked for the expectable currents and frequencies.
Currents:
Now there is a DC/DC converter. You did not mention it before.
Depending where you want to place the filter, the "2A" may be valid or not. The filter needs to be calculated for the current that runs through it.
Frequencies:
What "frequency" do you think is the problem?
* any frequency that is generated by the "digital electronics"?
* any frequency that is generated by the DCDC converter?
* any frequency (switching noise) that is generated by the relays and solenoids (sparks)?
* now that you showed a rectifier ... are you aware that a rectifier generates noise?
And are you concerned about "common mode noise" or "differential mode noise"
****
I fully agree with post#2.
And in post#6 you ask about a calculator. But every calculator needs values to be input.
So my idea is:
* if you want properly calculated values, you need to give input values first.
* if you don't have these values, one can not calculate filter part values. Neither one of us, nor a calculator. Then it's "guessing".
For me "guessing" is the same as "trial and error". While the one is a theoretical approach, the other is a practical approach.
Btw: someone recommended L and C. I can not say whether the values are useful or not. But generally I don't like undamped LC filters, because they generate resonances. Resonance may cause (uncontrolled) high resonance frequence amplitude. Be sure the resonance is damped somehow.
Klaus
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