Two unrelated questions: capacitors in circuits

Using Arduino General Electronics
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Hi All,

The first part of my question relates to a circuit I am builing following Nick Gammon's diagram for using a Max7219 chip with a common cathode 4 digit 7 segment display. In the cicuit there is this bit which has capacitors in parallel:

I realize that the capacitor to the right is an electrolytic capacitor, but the capacitor to the left is perplexing me! Would that be a ceramic disc capacitor? Also, when I am looking to buy these 0.1?F capacitors, if I look for ceramic capacitors there are ones that look sort of terracotta-coloured and called "ceramic disc" and there are others which are blue, and these are usually labelled as "ceramic". Is there any difference between these apart from colour? I've googled but perhaps I am not using the right search terms!

The second part of my question is again about another circuit diagram that I would like to follow and involves capacitors again. I have been testing an optical sensor for measuring RPM, but now I am going to test a couple of different Hall Sensors. The Hall Sensor I am most taken with is the TLE4905L (datasheet here). At the end of the datasheet, they have a potentially helpful circuit diagram, which looks like this:

The questions I am hoping people can help me with are:

  1. Are the parts in the circuit for a 5V setup like with the arduino? It's not clear to me...the bit about a "mainframe"(!!!) has me puzzled too :astonished: I take it that my arduino is the "mainframe"! :slight_smile:
  2. If I enable the arduino's internal pull-up resistor, does the 1.2k resistor in the circuit then become unnecessary?
  3. Am I looking for ceramic disc capacitors again for the capacitors in this circuit? Also, is the value of those capacitors OK to put in a 5V circuit?

I hope it is OK to ask all of these questions in one thread!

Candice

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if I look for ceramic capacitors there are ones that look sort of terracotta-coloured and called "ceramic disc" and there are others which are blue, and these are usually labelled as "ceramic".

Electrically, it shouldn't matter in this application. The blue "monolithic" capacitors might be better/stronger physically and/or have better/tighter tolerance.

  1. Are the parts in the circuit for a 5V setup like with the arduino? It's not clear to me...the bit about a "mainframe"(!!!) has me puzzled too I take it that my arduino is the "mainframe"!

Strange terminology... Yeah, that could be an Arduino.

  1. If I enable the arduino's internal pull-up resistor, does the 1.2k resistor in the circuit then become unnecessary?

Looking at the simplified schematic on the datasheet, you have an open-collector output. Yes, the Arduino internal pull-up should work. However, the higher impedance (the 20k pull-up) is more prone to noise pick-up. So if the signal runs a long distance, lower resistance may help with noise (i.e. false signals).

  1. Am I looking for ceramic disc capacitors again for the capacitors in this circuit? Also, is the value of those capacitors OK to put in a 5V circuit?

They should be fine. The voltage rating on a capacitor is it's maximum rating. Any ceramic or any ceramic-monolithic capacitors, will have a voltage rating higher than 5V and will be fine.

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Candice:
I realize that the capacitor to the right is an electrolytic capacitor, but the capacitor to the left is perplexing me! Would that be a ceramic disc capacitor?

Yes.

Candice:
Also, when I am looking to buy these 0.1?F capacitors, if I look for ceramic capacitors there are ones that look sort of terracotta-coloured and called "ceramic disc" and there are others which are blue, and these are usually labelled as "ceramic". Is there any difference between these apart from colour?

Blue ones are "Y-class" which means they're rated for use at mains voltages (eg. in power supplies). Apart from that they work just the same as the normal ones.

Candice:
The questions I am hoping people can help me with are:

  1. Are the parts in the circuit for a 5V setup like with the arduino? It's not clear to me...the bit about a "mainframe"(!!!) has me puzzled too :astonished: I take it that my arduino is the "mainframe"! :slight_smile:
  2. If I enable the arduino's internal pull-up resistor, does the 1.2k resistor in the circuit then become unnecessary?
  3. Am I looking for ceramic disc capacitors again for the capacitors in this circuit? Also, is the value of those capacitors OK to put in a 5V circuit?

See the sensor's datasheet for voltage ratings.
Probably.
You should be fine.

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Thanks so much DVDdoug and fungus - very VERY helpful info about the blue capacitors too.

Your help is much appreciated!

Candice

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