Basic AC Wiring Schematic - Page 1
Forum section: electronics / beginners

author: Larsson55
author_rank: Regular Contributor
timestamp: March 30, 2024, 02:33:31 pm
content: The attached indicates how I plan to feed power to a small control panel for my cnc mill. There are 4 DIN rail terminals for Line and 4 for Neutral. Line and Neutral terminals are separated and I have the jumpers between them as needed. The 120VAC feed line is 15A at the main electrical panel.Looks OK or it will blow the fuse?Thanks

author: AlbertL
author_rank: Regular Contributor
timestamp: March 30, 2024, 03:40:51 pm
content: Looks good to me. The only thing I'd suggest would be to feed the Line side of the indicator light off the terminal block, as you did with the Neutral. Electrically it's the same, of course, but mechanically it might be difficult to connect two (presumably) relatively large wires to the indicator terminals. By tapping off the terminal block, you could use smaller-gauge wire for the light.

author: calzap
author_rank: Frequent Contributor
timestamp: March 30, 2024, 03:55:37 pm
content: Unless your controller has it built-in, I’d use a starter that requires human action to restart in event of power loss or failure. These starters are readily available and not very expensive for 15 A. If the safety starter is part of the controller, I’d use a DPST switch rather than the SPST shown in the diagram.Mike

author: BeBuLamar
author_rank: Super Contributor
timestamp: March 30, 2024, 04:06:09 pm
content: Quote from: AlbertL on March 30, 2024, 03:40:51 pmAnd if the OP has enough terminals he should keep the one wire, one terminal practice. Putting more than 2 wires at one terminal is more difficult.

author: Larsson55
author_rank: Regular Contributor
timestamp: March 30, 2024, 04:30:12 pm
content: Very good comments and my thanks to all.Yes much better to feed the light from the DIN terminal and I will do it.I have no starter here however I have a BOB (breakout board) which connects all motors / spindle to the Mach3 software which runs the cnc mill. On that BOB there is a wiring method to wire the E-Stop as Hardware Disable and when I hit the E-Stop everything stops. For a Hobby cnc I think that's enough

author: Terry Bites
author_rank: Super Contributor
timestamp: March 31, 2024, 03:05:31 pm
content: Install a contactor so that all of the power on the DIN rails requires active restart. You can add your workshop emergency stops at the contactor too.An MCB+RCD, GFCFI (If you use Farenheit)seehttps://in.pinterest.com/pin/emergency-stop-button-switch-wiring-diagram-and-connection--719309371754038432/

author: jpanhalt
author_rank: Super Contributor
timestamp: March 31, 2024, 04:46:37 pm
content: Agree with T BThink of a situation where power fails for whatever reason - circuit breaker, lightning strike, downed pole, etc. You don't want a machine to restart when the mains come back on line.In most any setting, those outages, if not a simple breaker, may last from seconds to days. Require and active restart.

author: Larsson55
author_rank: Regular Contributor
timestamp: March 31, 2024, 05:47:37 pm
content: I only have 3 wires from my power supply BLK, WHT and GND (120VAC).The schematic posted has 4 wires going into the contactor. How should I wire the contactor?Thanks

author: jpanhalt
author_rank: Super Contributor
timestamp: April 01, 2024, 12:23:28 pm
content: It's actually fairly common. Almost all of my stationary tools are wired that way. Three are 3-phase based on VFD (all are wired to require a restart), the rest are single phase. I tried to find a picture of typical wiring, but Google is so infected with YT videos, that was futile.Can you post a link to the datasheet for the contactor you have (or scanned copy of the appropriate page)? In general, both ON and OFF switches are momentary. ON is N.O. and OFF is N.C. The ON activates a relay to start the motor and the relay is held in position by a "keep alive" circuit going through the OFF switch. When power is lost or the OFF switch is activated, that circuit is interrupted, the relay opens, and restart requires an action by the user.

author: calzap
author_rank: Frequent Contributor
timestamp: April 01, 2024, 05:19:34 pm
content: Quote from: Larsson55 on March 31, 2024, 05:47:37 pmThe diagram in the link is probably more complicated than you need. It’s for 3-phase and has an emergency off switch that sets off a buzzer. I’ve put a crude drawing below that shows the basic idea for single phase. I suggest you look at hook-up drawings for single phase motor starters that are available on the websites of major manufacturers. I have used ACI and WEG motor starters, but there are many others. Just be sure you use a listed (UL, ETL, CSA, TUV, etc) device. You’ll have to choose a relay coil voltage for the contactor when you buy it. Mains voltages of 120 or 240 VAC are common. 12 VDC and 24 VAC are usually available. If you are using a lower voltage, just be sure that the power source can provide the inrush current needed by the contactor coil.Most contactors have a compatible overload protective device as an option, and it’s highly recommended that you use one. Most are adjustable with regard to trip current. Be aware that even though the current to your equipment passes through the OLPD of a motor starter, it is not capable of interrupting the current flow directly. It’s not a circuit breaker. If a too high current is detected, it closes or opens a pair of signal contacts which can then, if wired properly, cause a stop action to the contactor.Mike

author: Larsson55
author_rank: Regular Contributor
timestamp: April 01, 2024, 07:04:24 pm
content: Thanks Mike for your time and the schematic. I will search to see what I can find and I have enough info now to proceed.