Suggestions for inductor for PCBA design

Moderators: violet, carmen.zheng

Post Reply
electronics559
Pre-kindergarten
Pre-kindergarten
Posts: 3
Joined: Wed Sep 12, 2018 9:25 pm

Suggestions for inductor for PCBA design

Post by electronics559 » Wed Sep 12, 2018 9:35 pm

Hi,

I am designing a PCB to have it manufactured by the Fusion PCBA Service. One part of the circuit is an ADC measurement of a mains AC voltage (of up to 230VAC). To do that, I am going to use the circuit suggested in this blog.

When I am selecting the components from OPL before doing my testing and design, I am not sure if the ones available in the Inductor part will fit the galvanic insulation that the coil in the circuit does.

Can you suggest me any component?

Thank you,

Electro A.D.

electronics559
Pre-kindergarten
Pre-kindergarten
Posts: 3
Joined: Wed Sep 12, 2018 9:25 pm

Re: Suggestions for inductor for PCBA design

Post by electronics559 » Wed Oct 03, 2018 4:39 pm

I also need a 33K and a 330K resistor, that I would prefer if they were SMD 1%.

They do not appear in the last 2017 OPL, is there a possibility to include them in the OPL?

tim948
Pre-kindergarten
Pre-kindergarten
Posts: 3
Joined: Wed Oct 03, 2018 11:19 pm

Re: Suggestions for inductor for PCBA design

Post by tim948 » Wed Oct 03, 2018 11:41 pm

What you are looking for is a transformer. I don't see any of those in the OPL. For selecting one I would look at digikey.

This link below is a shortlist of viable transformers that are rated for mains voltage... make sure you select your applicacble mains voltage 115 or 230... remember a higher rating will always work for a lower voltage.
https://www.digikey.com/short/jnhpwp

The next thing you need to figure out is what you want your winding ratio should be. Let's take this one for example https://www.digikey.com/short/jnhz7q

It has a secondary voltage of 24V(series) this means if your mains voltage is at 115V then the voltage on your secondary coil will be 24V meaning your ratio is 4.8:1. If you have the parallel version, 12V(Parallel) this means you will get 12V for a mains voltage of 115.

Series connection
Image

Parallel Connection
Image

Parallel will get you higher current ratings vs higher voltage. However for your sensing application either method is valid. You will just size your resistor divider accordingly for your A2D full scale value.

electronics559
Pre-kindergarten
Pre-kindergarten
Posts: 3
Joined: Wed Sep 12, 2018 9:25 pm

Re: Suggestions for inductor for PCBA design

Post by electronics559 » Thu Oct 04, 2018 4:48 pm

Thanks for your response tim!

The last days I have prototyped with a 230V to 6V transformer with two secondaries I found in RS-Online, so I can use one for Voltage measurement and one for digital frequency measurement (a 0V-3V3 square wave to GPIO). I have built a prototype PCB and all went fine.

Since the transformer has been proven to work properly and no OPL replacement is available, I'll be using this from RS-components or a similar one from digikey if it is less expensive. Do you know if the 33K and 330K 1% SMD resistors can be made available in the OPL or I should include them in the external provider's list?

Image
This is the circuit I've used, I hope it can help somebody in their projects as well

Thank you for your help.

Post Reply