Watts Intelliflow timer

Timer based dummy load for washing machine valve

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The Watts Intelliflow is a smart water valve for washing machines. It normally connects between your washing machine and the electric supply and senses the load of the washing machine to open the water valve only when the machine is in use. This isn't always ideal, so as an alternative, this device will supply a dummy load for a fixed period of time.

Watts and Intelliflow are trademarks of Watts Water Technologies, Inc. They do not support or endorse this project.

In most cases, this hack isn't necessary. But there are two cases where it is. Some washing machines require 240 volt power (if they are a single unit combination washer/dryer, for example). The Intelliflow uses / passes only 120 volt power. The second case is where you want more than one thing to be able to "request" water. In our case, our dryer has a steam function that requires water, so it's not enough for the washer alone to request it (and the washer is electronic, so there's no easy way to just leave it on while the dryer is running).

This project is based on Reboot-o-matic and the AC safety timer, but is rather simplified from those projects. There's just a button and a MOSFET switched load. The firmware will set (or reset) a timer for 6 hours whenever the button is pushed. While the timer is running, the MOSFET gate is pulled high, which switches on the power to a bank of 3 27Ω 1W resistors. Those impose a just-under 3 watt load on the power supply (when the load is off the power draw is perhaps 5 mW), which is enough for the Intelliflow to think that the washing machine is running and turn on the water. The Intelliflow is "smart," though, so just a constant load won't do. A real washing machine varies its load pretty frequently depending on what it's doing. We simulate that by turning the load on for 120 seconds every 223 seconds (prime so that it hopefully won't sync with any process going on in the Intelliflow). That's enough to keep the valve triggered. The input power is 5 volts and is supplied by a 5W wall wart that plugs into the Intelliflow's socket. There's a 2 pin connector for a normally open pushbutton (the ATTiny9 has an internal pull-up), and an indicator LED on another GPIO pin (since the load is cycled) to indicate when the water should be on.

Version 1 used an external DC supply, and it does work, but that design results in a more or less permanent vampire load. By doing just a little bit of extra work, we can eliminate that.

Version 2 starts with AC input on the board. The AC power goes to an AC-DC power supply module, but is switched by a solid-state relay. The SSR's LED is switched on by one of the GPIO pins of the Tiny9. To bootstrap the system, the button is wired across the SSR switching terminals. Pushing the button will turn on the power, and then the controller will activate the SSR and hold the power for the rest of the cycle. Once the cycle is complete, the controller will turn off the SSR and the power will die. The result of this should be a zero load (apart from any SSR leakage) when the system is idle. Version 3 adds a second SSR and moves the load to the AC side. A second SSR is required because the load is cycled on and off throughout the cycle to better simulate an in-use washing machine.

There is one caveat, however. System power won't be applied or removed instantaneously. As the power dies, the operation of the controller will pass through an unreliable stage, which can result in spurious RESETs. Of course, when the controller is reset, the first thing it does is switch the power on. The fix for this is to configure a brownout detector to hold the chip in RESET when the power is lower than a threshold. The Tiny9 includes a VLM - Vcc Level Monitor (why they didn't just call it a brownout detector like every other chip, I don't know), and the software will set it up to hold the chip in RESET as the voltage drops.

Watts actually sells something similar to this project. Unfortunately, their version only turns the water on for 2 hours at a time. I think 6 hours is more reasonable. Even if 2 hours was a reasonable period of time, the extra 4 hours isn't likely to hurt anything, since most machines stay off for days at a time. Also, their version is laughably expensive.

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  • 1 × Assembled timer board
  • 1 × 5W 5VDC wall wart with center-positive 2.1mm barrel connector
  • 1 × 3D printed case
  • 2 × 2-56 x 3/8" self-tapping screws
  • 1 × PR141C1900 SPST momentary pushbutton Electronic Components / Misc. Electronic Components

  • Heat

    Nick Sayera day ago 0 comments

    Well, stress testing of the V3 design showed some flaws. The 9.1kΩ resistors just get too hot and damage the board. So that's no good. I'm going to try 10kΩ because I have them handy, but there's probably a balancing act that's going to be necessary between getting too hot and pulling enough current through the Intelliflow to trick it into staying on. The previous board had just under 3 watts on the DC side and it wasn't perfectly reliable. Going from 9.1 to 10 kΩ drops the power on the AC side from 4.75 watts to 4.33 watts. The next most logical step would be to try 11kΩ, which would be just under 4 watts.

  • v3 build log

    Nick Sayer2 days ago 0 comments

    The version 3 boards came back and there were a couple of errors that needed to be worked around, but in essence it works. I'm going to have a 3.0.1 board made that fixes the couple of mistakes (a couple of clearance issues and moving one of the outputs from the TPID pin to the TPIC pin, which is less sensitive to loading).

    The v3 design uses two SSRs - one to hold the system power on for the duration of the sequence and another to switch the load on and off. The load is 3 9.1kΩ resistors in parallel, for a total of around 4.75 watts, plus another quarter watt or so for the LV side. The load is switched on and off at about a 50% duty cycle to try to fool the Intelliflow into thinking there's a busy washing machine there. But the goal of v3 has been reached - when the system is off the leakage of the power-hold SSR is practically zero.

  • v2 build log

    Nick Sayer10/11/2020 at 03:23 0 comments

    The version 2 boards came back. This design has the SSR and button power system so that there is no standby load. One thing I discovered while the boards were being made is that the Tiny9 has a Vcc Level Monitor system (again, why they don't call it a brownout detector, I'll never understand). At first glance, it doesn't seem terribly helpful, as if you configure it for the "high" RESET voltage (VLM1H) is "typically" 1.6 volts, while the safe area curve for the chip bottoms out at 1.8 volts (the VLM1L threshold is even lower at 1.4 volts typical). Why they made this choice I can't understand. However, in practice it appears to work ok (at least for one example). When the timer runs out, the SSR is dropped and you can see the power LED fade out over the course of about a second as the power supply filter caps bleed out. If the VLM wasn't working, I'd expect the chip to reset as the voltage dropped, and of course the first thing the firmware does is turn the SSR back on.

    So it appears that we don't actually need a hardware voltage watchdog chip separate from the VLM in the Tiny itself.

    The upcoming v3 board makes another change, and will likely be the final version. In this one we've traded a second SSR for a cheaper open-frame DC power supply that's rated for only 1 watt. The second SSR switches a power load on the AC side. 3 10kΩ 2W resistors form a ~4.3 watt RMS load (at 120VAC). The DC load (both SSRs and the power LED) top out at about 600 mW (the controller load is negligible). The power supply is supposed to be about 60% efficient, so that's another watt of load, so the combined total should be plenty to fool the Intelliflow.

  • Another direction

    Nick Sayer10/02/2020 at 21:50 0 comments

    I've been studying design for off-line switching converter chips to roll my own supply with the goal of making it smaller. If you do go that way, you can also do away with the optoisolated components, since the design wouldn't be isolated at that point. But the issue with that is that in order to operate the triac in quadrants 2 and 3 you want the positive supply rail for the LVDC side to be anchored on one of the AC legs and for "ground" to be 5 volts lower than that. With that configuration, driving the gate low would result in a negative voltage relative to the T1 leg of the triac, which gives us the operating quadrants we want. The alternative, driving the gate positive means quadrant 1 and 4, which is a problem because making a triac sensitive in quadrant 4 is hard (and can result in increased dV/dT sensitivity, which is bad).

    Another issue with the design is that putting the load on the DC side requires having a 3 watt power supply. Putting the load on the AC side just means that the DC supply only needs to do the equivalent of lighting 3 LEDs, which is less than half a watt (the load of the controller is minuscule).

    So for a sort of middle ground, I've made a board version that uses an open frame AC-DC supply that's fairly small and rated for 1 watt. The load is on the AC side and is switched by a second SSR (the first is the power supply holdfast). For 120VAC, 3 15 kΩ resistors will draw just under 1 watt each. This winds up being just a bit less than when the load is on the DC side (because of inefficiencies in the DC supply), but should still be visible enough to the Intelliflow.

    As before, the system will bootstrap with a pushbutton across the first relay's switch terminals. That will start power long enough for the controller to start up and activate the first relay, holding the power on for the duration of the timing cycle. The second relay will switch the load on and off to simulate washing machine activity. When time is up, the first relay will be turned off. As the DC supply voltage falls, the brownout detector will hold the controller in RESET until the power is too low to matter.

  • What the Intelliflow sees

    Nick Sayer09/22/2020 at 14:54 0 comments

    I took some measurements on the AC side using two different wall warts to see what the current flow would be with the load on and off. With the load off, the AC side sees about 100 mW. That's quite a lot, given that the theoretical DC load should be 800 µA or less at 5 volts (< 5 mW), but nobody ever said that wall warts were terribly efficient at low draw. With the load on, the AC side sees just over 5 watts of load. Given the theoretical DC load of about 2.7 watts or so, that's about 50% efficiency. Not... fantastic. The standby load will wind up being about a kW-hr per year. About the only way to make it any better would be an arrangement where the button would momentarily turn on AC power where it would be held on by an SSR for the timing duration. That's certainly possible, but it does complicate the design quite a bit (and raise the cost).

  • Another idea

    Nick Sayer09/19/2020 at 20:18 0 comments

    The board I have now does reliably start the intelliflow. Perhaps the solution is to cycle the load on and off in some pattern to keep the Intelliflow activated.

    the downside with the current hardware is that the activation LED is in parallel with the load, so modulating the load will modulate that LED. If this works, another rev of the hardware will be necessary to have a separate GPIO pin just for that LED. 

    EDIT: That seems to work. In fact, a duty cycle of about 50% seems to be about right. That's going to be good from the perspective of wasting power and from the board just getting hot from the dissipated energy.

  • First build report

    Nick Sayer09/18/2020 at 21:11 0 comments

    At first blush, the first iteration of the board - with just under 5 watts of dissipation does make an Intelliflow turn on. You have to give it time to turn off, though. Even unplugging the 5 volt wall wart doesn't make the power turn off right away. I believe this is because newer Intelliflows have a 15 minute timeout before they turn off.

    ~5 watts of dissipation, however, makes for a great deal of heat (and, of course, wasted energy). I am going to try to remove some of the resistors to see if the unit remains reliable without getting so hot.

    EDIT: Wow, it turns out two watts is enough. Who knew the Intelliflow was so sensitive? Well, now it looks like even 5 watts isn't reliable. Going to have to do more work.

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