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How to read schematic for PCBs

In a well-drawn circuit, high supply voltages should be at the top, and low ones at the bottom. Signals go from left to right (except feedback paths that have to go the other way). So start on the ...
• 19k

How to read schematic for PCBs

How do I learn to read a schematic and understand the function and how the circuit work? Practice and experience. Read books, take lectures and watch YouTube videos. Like people, every circuit is ...
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1 vote

The OP, captainretro, reports: "mapplejacks has answered my question in their comment": Yes, the bottom of this circuit should be your ground, which is where the ground pin gets connected ...
1 vote

Headphones with 3 pin TRS contacts are wired as follows: Tip: Left Ring: Right Sleeve: Ground (or common) for left and right. Thus the Sleeve connects to the arrow at the bottom, the same net where ...
• 137k
Accepted

What's the circuitry inside triac driver optocouplers?

Here is a simple possibility that looks somewhat similar to @Tim's die shot. T1, T2, T1', T2' are the opto triac. aand T3/T3' shunt the gate current when the voltage is more than the zero crossing ...
• 384k

What's the circuitry inside triac driver optocouplers?

The zero-crossing circuit looks like this: Source: MOC3061 - Zero-cross optoisolated triac driver : weekend die-shot | Zeptobars License: Creative Commons Attribution 3.0 Unported It appears MOC3061-...
• 27.4k
Accepted

How do the comparators in this circuit work? Do they compare the voltages between themselves? How do comparators generally work?

The two 3.3K resistors form a fixed voltage divider across the battery, producing half the battery voltage. Meanwhile, the LM7808 provices a constant 8V, that won't change (unless the battery is ...
• 19k

How do the comparators in this circuit work? Do they compare the voltages between themselves? How do comparators generally work?

The two comparators measure the voltage in 3k3 -s middle point and comparators output gets active if one of voltage boundary is found performing the change of NOR latch state. If no boundery is found ...
Accepted

Diode and bipolar NPN transistors orientation not correct, says JLCPCB

I guess what causes the populated view to show up inverted, is that the pick and place file generated from KiCad ends up 180° rotated for polarized components *. Therefore, they fix this to adjust the ...
• 19.6k
Accepted

Do non-polarized capacitors need to be in any type of orientation?

Both of those capacitors are polarized and must be installed in the correct orientation or they will go up in flames. You have specified tantalum electrolytic parts which are different from those in ...
• 384k
1 vote

Do non-polarized capacitors need to be in any type of orientation?

Well, they need to be in some kind of orientation where the contacts touch the pads... If they're non-polarized (probably ceramic) the terminals can be positioned either way. Unfortunately, the spec ...
1 vote

NE555 + CD4017 Airplane Strobe Light with LDR

Other answers have noted the problem, but I'd suggest an alternative solution: have the right side of the LDR connect to Q8 of the 4017 rather than VDD. That would ensure that no matter where during ...
• 46.4k

NE555 + CD4017 Airplane Strobe Light with LDR

The LED is getting stuck on because you're not also resetting the CD4017.
• 170k

NE555 + CD4017 Airplane Strobe Light with LDR

There should be a pull-up resistor (say 10k) between the 555's Reset (pin 4) and Vcc. Also add a decoupling capacitor (4.7uF) between Vcc and ground close to the 555's pins 1 and 8. You need to hold ...
• 521

How to understand schematic circuit diagrams in functional safety

These kind of standards like to make simple things as complicated as possible... even though it is well established that increased complexity leads to more errors. What you need for a "reduntant&...
• 18.7k
Accepted

How to understand schematic circuit diagrams in functional safety

What do the dashed lines mean? In the case of Figure 2, Q1 they show the mechanical connection between the coil and the contact. This is a bit redundant as both are labelled Q1. In the case of the ...
• 171k

How to understand schematic circuit diagrams in functional safety

The dashed lines represent physical interconnects, either microswitch actuator to contact (B1 and B2),or relay coil armature to associated NO and NC contacts (Q1 and Q2). The "separate" ...
• 6,196
1 vote

PCB from circuit diagram

The R##, D##, C##, etc. are known as Reference Designators. ...
• 326
1 vote
Accepted

Removing HSE backup crystal from ST RF module

The circuit you show is not backup low-power and low-frequency clock, but it is main precise clock refered as HSE (High-Speed External). While MCU itself can work without it, the RF module use it as a ...
• 350

So the 50Hz (and harmonics) sound IS there ONLY when the photodiode is NOT covered? Then it is responding to mains related variation in light intensity coming from your desklamp and other lighting. ...
• 6,604

The quad op-amp has two unused elements. Vout should be tied to IN-. IN+ should be biased to VCC/2 and capacitivily bypassed to VSS. I see no power supply decoupling. Quad and dual op-amps require ...
• 13.6k
Accepted

How should I interpret this DP3T switch diagram?

It's hard to know why they wouldn't make this information very clear. From experience several decades ago I would think it's something like this: simulate this circuit – Schematic created using ...
• 171k
Accepted

SWD Connection to MCU and Appropriate Configuration for Reset Pin

If your only goal is programming under controlled environment, there is no need to have any special arrangements. Unless it is expected that using the programming header will be exposed to users, like ...
• 137k

What is the purpose of these Schottky barrier diodes connected with reverse polarity between the Vin line and gnd?

These are flyback diodes that shunt inductive kick-back. A good idea whenever there is inductive filtering on the load and/or the parasitic inductances combined with high load cause concern.

What is the purpose of these Schottky barrier diodes connected with reverse polarity between the Vin line and gnd?

Those aren't diodes for general protection as much as they are for keeping PL9 and the VIN+ connector out of trouble when VIN+ gets disconnected, by providing a short-time alternative current path.
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What is this weird split circle symbol in a schematic?

It's a solder bridge, they look like this on a PCB: Source: https://diptrace.com/forum/viewtopic.php?t=11687
• 78k

What is this weird split circle symbol in a schematic?

That would appear to be a solder jumper (aka solder bridge). On the circuit board there will be two pads like that and you can either leave them open or put a blob of solder (or a short piece of wire) ...
• 19.6k
1 vote
Accepted

Meaning of 'POL' on component?

Power On Light. And I think a circle with the 4 lines coming out of it is a standard electrical wiring symbol for a light.
• 10.3k

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