There are some capacitors (10 \micro F and 4.7 \micro F) which are limiting my development of Raspberry Pi Hats because they are provided only with tolerance of 10% or greater.
It seems that the physical components which they use are difficult to extract from the nature, making their price if available high.
I would like to understand how you can replace such capacitors with low-cost components.
My current design requires me in using the expensive capacitors.
I think how you can replace those with cheaper ones without altering the other components of the board. I can easily make the board bigger if necessary for cheaper replacement.
How can you replace tight capacitors with low-cost components for better tolerance?
Best Answer
You are looking at this problem from too low a level. It's not about how to replace accurate capacitors with cheaper ones, but rather how to avoid requiring accurate capacitors in the first place.
You haven't said what the capacitors with the tight tolerance are for, but think about other ways to achieve the same thing. For example, if the cap is one component of setting the frequency of a filter, perhaps you can move the filter frequency so that you still get the minimum you require with ±10% capacitance instead of ±2%. If this is a DC blocking filter for audio, for example, then instead of a tight filter at 20 Hz, a sloppy filter nominally at 16 Hz will likely do.
For precision filters, consider doing it digitally. Even low end DSPs can do a much better job on audio than analog filters. The filters can be tighter and more accurate than even what high precision capacitors can provide.
Another thing to do is to look at the role of each cap carefully and make sure you really need the tight tolerance. If it's just for bypassing or to smooth a power supply, accurate values are not required.
In general, think about ways to solve the problem by using components that are cheaply available at high accuracy. Time is something we can measure/generate very accurately for the money. A $.20 crystal can to 50 PPM. Resistors can do 1% without a cost premium, and can get much better for a bit more money. Note that anything you do in a digital processor relies on time and little else. This is why signal processing is done in a processor when the bandwidth allows this.