Electrical Rules Checker (ERC) problem [KiCad] - Page 1
Forum section: electronics / general

author: AxelVega
author_rank: Newbie
timestamp: September 21, 2019, 10:13:33 pm
content: Hi, guys!!! I´m a beginner in KiCad and I'm trying to make a circuit (instrumentation amplifier), but when I run the ERC in order to create a Netlist that would allows me to make the PCB or even in order to simulate my circuit with Spice, I have 4 problemsThe ERC gives me 4 mistakes. In the first and second, it has to do with the input of my circuit, what I'm trying to do is to set them as an input but apparently I was mistaken set them with the +12V and -12V respectively component, so I changed one of them to Vcc but the mistake is still the same. The third mistake occurs in the ground that is connected to the resistance R8. Finally, the fourth mistake occurs in the V- entrance of the OPAMP U1, that i what to power it with -12V. I cannot explain this last mistake because the other OPAMP U2 has no mistakes and I did the same connection.PLEASE HELP METHANKSNotes:*I saw that using a PWR_FLAG you could set the pins as Outputs but in my case those pins are 12V inputs.*Every single connection is well-connected, I already connected them many times.*Sorry if my english level isn´t good enough, it is not my native language.

author: ElektroQuark
author_rank: Unknown
timestamp: September 22, 2019, 12:35:01 am
content: Read again about the use of the power flag.

author: tox3
author_rank: Contributor
timestamp: September 22, 2019, 05:13:50 am
content: Adding power flags to VCC and GND nets would solve all errors.If your schematic has pins with type Power in, they should be connected to components with pin type power out for example linear regulator.If you connect of board power, then power flags should be used.

author: poeschlr
author_rank: Regular Contributor
timestamp: September 23, 2019, 08:11:47 am
content: For some reason i do not see your screenshots (probably some firewall problem at my end). Fro the other answers i gather that you have trouble with power supply pins.KiCads ERC checker is purely net based. One of the checks ensures that every net with a power input pin is powered by a power output pin. Sadly the net based restriction does not allow the checker to follow a power supply line over passive devices like fuses, ... To solve this one needs to add a power flag at the output of this passive device.Another problem area is that you most likely use a generic connector symbol as the main supply for your pcb. This generic connector of course does not tell kicad that it is a power supply so you also need to add a power flag to the supply lines.More details seehttps://forum.kicad.info/t/errtype-3-pin-connected-to-some-others-pins-but-no-pin-to-drive-it/10946/

author: spudboy488
author_rank: Regular Contributor
timestamp: September 23, 2019, 11:41:06 am
content: VCC being connected to the ground pin of the OP-AMPs (Pin 4)?

author: grbk
author_rank: Contributor
timestamp: September 23, 2019, 01:26:45 pm
content: Problems I see:1. You'll need power flags on all of your power rails, which means GND and VCC in addition to the one you have on +12V. It's unclear to me why you have VAA attached to the output but in any case I don't think you'll need to add a power flag on that net (Kicad should consider it to be driven by the opamp output).2. +12V appears to be disconnected from R2 at top left (there's a break in the connection)3. This won't cause ERC errors, but you have VCC on both V+ and V- for all of your opamps. You'll need a negative supply on V- for this circuit to work.