FAULTS IN SCHEMATIC - Page 1
Forum section: electronics / projects

author: gsingh11
author_rank: Contributor
timestamp: February 03, 2023, 04:30:26 pm
content: Hi, I just made a new schematic for my upcoming project. i am looking for any mistakes in it. if you find any errors please let me know so I can improve it.[/img

author: jmelson
author_rank: Super Contributor
timestamp: February 03, 2023, 05:18:46 pm
content: The diode on the solenoid valve (D7 or is it D?) is backwards.Jon

author: mariush
author_rank: Super Contributor
timestamp: February 03, 2023, 05:25:56 pm
content: You're using LM2596S-12 on schematic which makes it sound like it's a fixed output voltage 12v version, but it seems like it's for 5v because power goes to the Arduino.But it also goes to the relays - G8N-1U is a 5.5v max part... don't know why you don't use 12v relays.It's really debatable that you need a switching regulator to produce 5v, because that sensor HC-SR04 consumes maybe up to 15mA , the Arduino a few mA, and the leds connected to the Arduino maybe 7-10mA each (due to the two 330 ohm resistors) ... so I don't see your project needing more than 100mA on 5v (edit: if we don't include the relays) and in that case a linear regulator would be almost as efficient as that LM2596 regulator.edit : if we include the relays, those probably consume around 40-50mA when engaged, so let's add another 100mA worst case scenario, so at most 200mA12v - 5v at 100mA or so with a linear regulator will be around 40% efficiency, with LM2596 will be around 75% efficiency but at several times the cost.If you want efficiency (90% and higher) get a better switcher IC that runs at higher frequencies and has inductors and everything "optimized" for 100-250mA.TIP120 is a npn darlington transistor, 5A , with hFe minimum 1000mA ... it's overkill for a relay that consumes 50mA or so while turned on.You could have easily used something like FCX491 (hFe 300+) or FMMT491 (hFe 100+) or even MMBT555x which has a hFe of around 50, and just use higher base current like 5mA or so, which is something Arduino can do, for example just go down to around 100-470 ohm instead of 1 kohmSeems like you have plenty of pins on the atmega ... maybe it would be simpler and easier to just have one led per pin and if you want to lower power consumption you can always loop and pwm them to reduce power consumption.I didn't check if you actually wired that LM2596s correctly - assume you're gonna buy one of those ready made units from ebay which will have fake / cloned chips and not proper lm2596s

author: fourfathom
author_rank: Super Contributor
timestamp: February 03, 2023, 05:29:12 pm
content: It also appears that the relays K1 and K2 are not correctly wired to the pump and solenoid. I see no ground connection, just the +12V.

author: GigaJoe
author_rank: Frequent Contributor
timestamp: February 05, 2023, 11:17:22 pm
content: i may assume 12V would be from wall plug like 1A 12Vmeans add caps for 12V filtering5V linear for arduino , it was mention , and 12V relay , for emiter base recommended shunt resistor in a few K, consider that digital low maybe sufficient to open relay transistor, means you need a diode or resistor divider for increasing level when it trigger . you may consider TTL logic mosfet as a switch (IRL510 , IRL3803).modern led diodes usually work at 1ma , means high 5V over 330 ohm around 15ma ; consider a few Khom resistors for ledconsider fail safe circuit if by errors pump started but solenoid not, or whatever ( no idea of logic) if Arduino or anything misbehave ( like an additional TLL logic)consider fail safe for 12V an 5V like zeners if voltage increase for some reasons, (lighting spike)consider an initial state of ports when arduino just started , and unknown status of ports, you may need RC to delay command to management transistors.consider a second mechanical switch for full \ empty as a failsafe if you sonar misbehave.

author: SiliconWizard
author_rank: Super Contributor
timestamp: February 05, 2023, 11:50:32 pm
content: It hurt my neck.

author: Damianos
author_rank: Frequent Contributor
timestamp: February 06, 2023, 10:19:43 am
content: Additionally to what is already mentioned, the 12V relays will not work properly on 5V, if they work at all.EDIT: it is already mentioned herehttps://www.eevblog.com/forum/projects/faults-in-schematic/msg4679473/#msg4679473