Draw a small circuit, test it immediately, then add the next part. This makes each wire easier to understand and faults easier to find while the circuit is still simple.
1. Give your circuit one specific job
Suppose you need to control a contactor called KM1. A contactor switches power to a load; here we focus only on controlling its coil.
The requirement is short: press Start and KM1 picks up; release Start and KM1 stays energized; press Stop and KM1 drops out. Write this beside the drawing so you know what each test is checking.
Do not rush to add timers, indicator lamps, or several interlock branches. Finish the Start–Stop circuit first to build a sound foundation.
2. Prepare the right components
You need a control supply, Start and Stop buttons, the KM1 coil, and a KM1 auxiliary contact. The auxiliary contact opens or closes with the coil and keeps the circuit running after you release Start.
Start uses a normally open contact, or NO: open when released and closed when pressed. Stop uses a normally closed contact, or NC: closed when released and open when pressed. Understanding these resting states covers a key part of reading the circuit.
Choose symbols with the right function in the EleRun library. Wires must attach to device terminals; a line that merely sits near a terminal does not make a connection.
3. Draw the main path, then add the holding branch
Open EleRun, sign in, and create a drawing. Arrange devices in a readable order from the supply to the coil. Leave space beside Start for the holding branch.
Once connected, read the path aloud: supply through Stop, through Start, to the KM1 coil, then back to the supply. Following the complete path helps reveal missing connections.
- Place the supply, Stop, Start, and KM1 coil on the drawing.
- Connect the main path: supply → Stop → Start → KM1 coil → supply return.
- Place a KM1 NO auxiliary contact in parallel with Start. Connect its branch after Stop and before the coil.
- In device properties, assign the same KM1 tag to the coil and auxiliary contact. The tag links them; writing KM1 in a nearby text note does not replace this setting.
- Check wire endpoints and device names before testing.
4. Press the buttons and watch what happens
Switch to Run. Press Start, release it, then press Stop. Do more than watch the coil light up or change color: check that it stays energized after Start is released and drops out when Stop is pressed.
If releasing Start stops the circuit, inspect the holding branch. If Stop does not stop it, look for a branch feeding the coil around Stop. Change one thing at a time and test immediately so you know what actually helped.
Use Check to review faults EleRun detects in the drawing. After addressing warnings, run the Start–Stop sequence again to verify behavior. Before closing the page, wait for the save status to confirm synchronization.
5. From your first circuit to everyday use
Once you understand this small circuit, try adding an indicator lamp or a run-permission condition. Adding and testing one part at a time is easier to follow than drawing an entire page and troubleshooting from scratch.
EleRun lets you draw and test directly in your browser. With supported devices, you can see the effect of a change in the drawing you are working on.
For a drawing used in construction, you still need to select devices, conductors, and protection for the actual requirements. Simulation helps explain how the circuit works; installation ratings need separate verification.
To understand why the circuit keeps running after Start is released, read the Start–Stop holding circuit article next. It includes a diagram and situations you can try yourself.
ELERUN LAB · TRY IT YOURSELF
Keep the drawing, break one connection
After your first Start–Stop circuit works, record three states: idle, after releasing Start, and after releasing Stop. Keep an untouched baseline copy.
- In the test copy, disconnect only one end of the KM1 auxiliary contact's wire near the coil; keep Start and Stop.
- Press and release Start. Does the circuit still hold? Zoom in to locate the wire end that is no longer attached to a terminal.
Compare your reasoning
Start can still feed the coil while pressed, but after release the auxiliary branch is open, so there is no holding path. Reattach the wire to the correct terminal and test both Start and Stop, not just the running state.
This exercise teaches how EleRun interprets connections; it is not an installation drawing.
6. Frequently asked questions
Do I need to sign in to read the article?
No. You can read articles and view diagrams immediately. You need to sign in to create and save drawings in the application.
Which circuit should I start with?
A Start–Stop holding circuit is a good first choice: few components, familiar actions, and clear results to compare.
