====== Tom Boon's Sofa Control Switches ======

3/25/2022 - Tom purchased a large sofa-recliner set for his living room a couple of months ago. The switch panel for the right chair was damaged and wouldn't work. The switches were small metal pieces that form a touch-sensitive circuit. I built a box via 3D printing with switches in it as a replacement.

There are two similar but different "systems," one for each chair. The working one has conventional switches on the left side. Both systems have a 24-28 VAC adaptor. The control circuitry then controls the leg and head rests, in and out. This assumedly works by changing the polarity.

I wired my switches into the touch-sensitive circuit, and it did not work reliably. I think it was expecting AC high-impediance current, so what I did was different. I took detailed pictures of the circuit to see if I can wire my switches in to the relays more directly (bypassing the touch-sensitive part).

==== Bridge Rectifier ====

{{ :tom:bridgerectifier_kbl410.jpg |Bridge Rectifier}}

This proves that the adaptors are 24 VAC. A filter capacitor is mounted on the other side.

==== Control Relays ====

{{ :tom:relay_973-24vdc-sl-c.jpg |Relay (4 of them)}}

==== Relay Schematic ====

The relay on the circuit board is a 973-24VDC-SL-C. This relay schematic is similar to a 973-24VDC-SL-**A** which is SPST type instead of the desired SPDT (even though the N.C. connection is not used).

{{ :tom:relayschematic.png |Relay Schematic (bottom view)}}

Here is the control board for the "system" with touch-sensitive controls. Labels are from my deduction, schematic is unavailable.

{{ :tom:controlcircuitboardwithannotations.jpg |Circuit Board with Annotations}}

Looks like the solution is to pull the other Coil lead to ground.