INTENDED FUNCTION: In position 1, the voltage will feed the speed controller to modulate voltage to the Logic Controller, which will serve to modulate speed of the Basket Motor from the programmed output of the Logic Controller.

Position 2 will still use the Speed Controller to modulate voltage, but will bypass the Logic Controller to indefinitely run the Basket Motor and simultaneously run the Drying Fan as well.

Much thanks for the insight in my previous question about relays. I'd like to isolate part of my circuit and get some insight into why I might be having problems. The circuit contains 3 8-pin relays, 1 voltage regulator, 1 logic controller, 1 DC speed controller, and two DC motor loads.

Within this circuit, there are 2 functions: Clean and Dry. For the time being, I want to ignore the Clean function because I recognize at least one of the problems there. So looking at the Dry function (which feeds through the currently open position of the Fx Switch and into the Drying Relay).

The problem I have is when I adjust the speed controller's built in potentiometer knob much farther beyond the lowest setting, I start getting some rhythmic clicking from my Drying and Fx Relays and my Drying Fan slows down to nearly nothing. What I'm expecting to happen is the sustained operation of the Basket Motor (with Speed Controller affecting its speed) and the full unaffected operation of the Drying Fan.

I really wanted to solve this myself, but I'm convinced now that there's a problem related to how I have things setup that is preventing expected operation of this circuit.

I wanted to add some info that will surely be asked.

Basket Motor: 24V 6.25A

Drying Fan: 24V 0.1A

Fx Switch: Rated for 250V 16A

Most wiring is 22 AWG, but some is larger. I don't believe voltage drop is an issue, all of the components are very closely located to each other, with the run of wiring being on average about 6". But I am curious about the potential need for flyback diodes. All 3 of my relays are in close proximity of each other, but I know virtually nothing about this. I'll be reading up on this, but if anyone else suspects this to be a potential issue, I'd love to hear about it. enter image description here

Response for GodJihyo's answer:

I agree with you. After some consideration, the only relay I actually need is the Fx relay. I'll expand on some functionality so that context can be applied where you currently have assumptions.

The Logic Controller is a ready-made circuit board that controls a DC motor (via programming inputs) to determine amount of time to drive a motor forward, time to stop, and time to reverse the motor.

With the Cleaning and Drying relays removed from the circuit, in position 2, I would expect the Fx Switch to energize the coil of the Fx Relay and bypass the Logic Controller for uninterrupted powering of the Basket Motor. Position 1 would allow for the NC outputs of the Fx Relay to feed into the Logic Controller and allow the program to run and operate the Basket Motor as intended.

I will redesign the circuit and come back with an update. Thank you for your input. I'm a mere hobbyist, so I have much to learn.


I've actually come full circle to realizing why I initially had the relays in place from the start. It is because the path from the Fx switch needs to go to the input of the Speed Controller in both positions. Without a relay to manage the voltage via the NO contacts, there's no way to separate the voltage based on the Fx switch. For example, here's what I've got so far before I realized the problem:

enter image description here

So no matter which position the Fx switch is in, the Fx Relay will have its coil energized. Now I'm sure there's a solution to this that doesn't involve 2 more relays like I originally had, but this is why they were there originally. Very eager to hear further input on this.

  • \$\begingroup\$ I would prefer 18 AWG wire for the 6.25 A connections. What is the current rating of the 24 V supply - it sounds to me like the supply may be shutting down due to overcurrent. Also, as I said in a comment to your previous question, the Drying relay is unnecessary - its contacts are only closed when the switch is in the Drying position. \$\endgroup\$ Feb 6 at 2:40
  • \$\begingroup\$ The supply is 8A. I see what you mean about the Drying Relay, I believe you're right that it could actually be eliminated. Good catch. Overcurrent: I assume that means a greater demand from the supply than it can produce? I thought I had added up everything and the 8 was sufficient. The logic controller is powered by the 5V at 1A. \$\endgroup\$
    – tinkering
    Feb 6 at 2:49
  • \$\begingroup\$ Motors can draw much more than their rated current when starting. To see if the supply is shutting down, measure the supply voltage while you try to start the basket motor. \$\endgroup\$ Feb 6 at 3:26
  • \$\begingroup\$ With your Update 1 circuit, the FX relay will be energised in both positions of the FX switch, so can be removed. The motor will be fed from the speed control at all times, and the Logic Controller will never get 24 V. \$\endgroup\$ Feb 6 at 4:14
  • \$\begingroup\$ Yes, that's basically summing up what I wrote below that updated schematic. I don't want to remove the Fx switch, I want it to work. Maybe I've gotten ahead of myself and haven't adequately explained intended function of entire circuit. I will add that to top of original post. \$\endgroup\$
    – tinkering
    Feb 6 at 4:23

2 Answers 2


I think this will do what you want:


simulate this circuit – Schematic created using CircuitLab

  • \$\begingroup\$ It certainly seems like it would do what I want. It's missing the main power switch, but that's easy enough to add. I believe where your design differs the most is by "reversing" the relay. That's really quite a clever solution I hadn't thought of. I'm disappointed I couldn't come up with this on my own, but that's part of learning I suppose lol I really appreciate your help on this, thank you. \$\endgroup\$
    – tinkering
    Feb 6 at 5:39
  • \$\begingroup\$ I had almost the exact same schematic but the CircuitLab editor wouldn't let me save it. It crashed and I had to reload the page, saw this and said "oh there it is, oh no wait...". lol. \$\endgroup\$
    – GodJihyo
    Feb 6 at 6:22
  • \$\begingroup\$ I was finally able to get the time to rewire, and after diagnosing a few issues: I burned out my speed controller somehow OOPS, got my NO/NC connections mixed up, and polarity on my fan backwards (female connectors I ordered came wired backwards)...this circuit works brilliantly. So thank you. I definitely learned something. \$\endgroup\$
    – tinkering
    Feb 12 at 21:17

I've taken the schematic and highlighted the wiring for each switch position with different colors for the different voltages. The shades of blue are the negatives, I suspect these could all be combined into one single ground node.

In position 1, the 24 V goes through the cleaning relay which does basically nothing but add a failure point to the circuit. It then goes through the speed controller and then through the fx relay which again does nothing. The output of the speed controller then goes to the basket motor and to the outputs of the logic controller which hopefully don't mind having voltage applied to them. The logic controller gets 5 V, but there is not +24 or -24 going into it, so it appears to do nothing. weird circuit position 1

In position 2, 24 V goes to the drying fan. It also goes through the drying relay, which again does nothing, and into the speed controller, the output of which goes through the fx relay to the basket motor, again the logic controller seems to be uninvolved other than having voltage placed on it's outputs. weird circuit position 2

So basically both positions turn on the basket motor through the speed controller, and position 2 also turns on the dryer motor. The rest of the circuitry is just redundant.

The whole thing needs a complete redesign, start with a specification of what it should do, eliminate the unnecessary parts, and then run it by us again.

  • \$\begingroup\$ This is great. I've edited my post to adequately address this. \$\endgroup\$
    – tinkering
    Feb 6 at 3:24
  • \$\begingroup\$ I've added more information in UPDATE 1 of my post. \$\endgroup\$
    – tinkering
    Feb 6 at 3:59

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