0
\$\begingroup\$

I purchased an inexpensive electric hoist off Amazon with the intention of partially replacing its control circuits so that it can controlled via ESPhome.

There are only 2 buttons on the control box. This hoist has 3 operating modes:

  1. Off (no button pressed)
  2. Forward (Forward button pressed)
  3. Reverse (Reverse button pressed)

Here are pictures of its existing control circuit: enter image description here

I believe the AC motor is a Permanent-split capacitor motor based on how the capacitor is permanently wired to one of the motor winding in series.

Based on the above photos, I drew the following schematic:

enter image description here

Does this schematic look correct? I am very unsure about it.

Since the original control circuit uses a single DPDT On-Off-On switch, I just assumed (without much evidence) that it can be replaced by two SPDT relays.

But when I sit down to actually draw the the new relay control schematic, I become stuck. I am struggling to find a way to replace the original one DPDT On-Off-On switch with two SPDT relays.

If I relax the restriction and allow myself to use 3 relays, then the problem becomes easy again, but a two relay would be more elegant if it is indeed possible.

\$\endgroup\$
3
  • 1
    \$\begingroup\$ A three position push switch? How does that work, exactly? \$\endgroup\$
    – Finbarr
    Commented Jun 26 at 13:14
  • \$\begingroup\$ It's kinda hard to explain using words, so here is a datasheet for an equivalent device. Basically take a two-pole, 3-throw rocker switch, and remove/ignore the middle throw (off position), then expose the two ends of the rocker as separate push buttons. \$\endgroup\$ Commented Jun 26 at 21:18
  • \$\begingroup\$ @Finbarr Here is another equivalent device. Their description is on the mark: "DPDT On-Off-On, Functions like two separate SPDT switches operated by the same actuator. Only two loads can be On at a time. " \$\endgroup\$ Commented Jun 26 at 21:22

2 Answers 2

1
\$\begingroup\$

The application would require two single-phase, 110 V ~, 12 A, AC-7B duty, modular contactors with 24 V DC coil and (1 NO + 1 NC) contacts.

Here's the schematic.

enter image description here

The limit switch is not shown.

\$\endgroup\$
2
\$\begingroup\$

I don't think your schematic is right- the top switch would do nothing.

Something like the below is what I expect could work (limit switch(s), thermal protection etc. not shown):

schematic

simulate this circuit – Schematic created using CircuitLab

\$\endgroup\$
3
  • \$\begingroup\$ the top switch turn the motor off in the middle position \$\endgroup\$ Commented Jun 26 at 12:07
  • \$\begingroup\$ The connection is already broken from the bottom switch. \$\endgroup\$ Commented Jun 26 at 12:22
  • \$\begingroup\$ ah yeah, it is. maybe it has something to do with operating the brake? \$\endgroup\$ Commented Jun 26 at 12:36

Not the answer you're looking for? Browse other questions tagged or ask your own question.