Designing a General Purpose Heat Pump Controller

[jeff5may]

Originally Posted by stef110

@ jeff5may

What do you mean by simple? don't you think that if we made a paper tutorial with pictures, then i think that the can solder there own print?

The arduino nano has his own usb port but the same pin layout as the mini pro. I used in other project it is easy to use.

stef

Yes, you should be able to load our sketch into a Nano and have it do the same thing. However, I wouldn't expect a 5th grader to be able to solder pins and breadboard and debug the thing to make it work. To someone with an intermediate or expert skill set, the task would be trivial in nature, but to a beginner or novice it would spell disaster.

The old-timers, with their "trade secrets" and "license necessary" attitudes are becoming a dying breed. With the advent of the internet and the information age, one can quickly look up how to do anything. There are multiple websites that operate just for this purpose.

However, just because you can look something up and be shown how to do it doesn't mean people will follow through. The reason why is simple: Joe Average is too lazy. Just look on any of the DIY websites that sell stuff. The kit forms of projects will always be readily available, while the more expensive, ready to use, prebuilt kits will more often than not be sold out. Who wants to solder and assemble when the finished product is available for 50% more?

My intent here is not to sell prebuilt kits, but assemble a short list of components that will work with a minimum of manual assembly. Someone should be able to go to radio shack, amazon or ebay and buy a couple of devices and have our basic set of components in a bag or box in ten minutes.

For example, from RadioShack:

• generic usb (arduino to pc) cable
• arduino uno r3 module
• Seeed Grove-Starter Kit for Arduino
• Seeed Relay Shield V2.0

For a grand total of around $100, buying name-brand stuff, at a store notorious for its high markup prices, a novice could rig this list to an ATX power supply harvested from any old computer and make a finished product. Granted, there would be some figuring involved in adapting the parts to the heat pump, but it could be done without much mayhem involved.

Again, from amazon:

• SunFounder 4 Channel 5V Relay Shield Module for Arduino UNO
• SainSmart C00 Kit with LCD Keypad Shield + UNO for Arduino UNO MEGA Duemilanove
• SunFounder Project Universal Starter Kit For Arduino UNO R3 Mega2560 Mega328 Nano
• 365buying DS18B20 Temperature Sensor - Waterproof Digital Thermal Probe Sensor DS18B20 (more than 1 piece)

Same thing, only cheaper grand total.

[buffalobillpatrick]

Don't we need more than 4 relays?

I just wrote a sketch that should work with that Amazon flow sensor, timing the pulses.

What flow sensor is better? They look to be $$$ for name brands.

[AC_Hacker]

Originally Posted by buffalobillpatrick

...I just wrote a sketch that should work with that Amazon flow sensor, timing the pulses...

Is your flow sensor required for fluid flow rate, or to verify that the pump is working?

-AC

[buffalobillpatrick]

A/C I thought it was your idea?
See pg1 post #2
That list also shows 6 relays.

[Ormston]

Originally Posted by buffalobillpatrick

Don't we need more than 4 relays?

I just wrote a sketch that should work with that Amazon flow sensor, timing the pulses.

What flow sensor is better? They look to be $$$ for name brands.

I've not managed to source anything better yet, mine was fitted last October and works most of the time except for the sticking.
It may be because I only use the low end of the range 7-14 LPM. I,m using it as a flow switch for my cheap and nasty ashp as well as measuring the heat output in near real time with the help of a pair of waterproof ds18b12 temp sensors.

[jeff5may]

The 4 outputs for relays are:

• outdoor fan/ground loop pump
• indoor fan/hydronic loop pump
• compressor
• crankase heater/reversing valve

To make the reversing valve and the crankcase heater work together, off the same relay, they will both need to be active in heating mode. If they take different voltage, wire a transformer in.

This leaves room for customization. For example, if you wire your outdoor fan to the compressor, they will both run with each other. Then you can have a separate crankcase heater relay.

[NiHaoMike]

It would be a good idea to add spaces for extra relays.

[buffalobillpatrick]

I don't see the need for flow sensors, except for trying to measure COP or pumps in series.

I have installed dozens of pumps in hydronic systems & it becomes obvious pretty quick if a pump stops working, much tougher though when they are in series.

I would think that crankcase heater should be turned off when compressor starts.

Why can't both source & load water pumps be controlled by 1 relay?
Do they need to ever run independently?

Why can't the source & load water pumps AND compressor be controlled by 1 relay?

[jeff5may]

OK, now for more conventions and constraints.
With the wide variety of configurations planned, it is possible to overload the Arduino board quite quickly. So I'll put out some rules. Feel free to comment on them, as they will probably change.

The Arduino chip and logic components attached to it must draw currents from the board. Input and output devices must also draw currents from pins on the chip. These currents must not exceed 20 mA per pin. The combined loads of all attached logic devices must run off the regulated 5 Volt pin when the unit is in standby (main power off). This includes shields and peripheral components such as sensors, displays, optocouplers, buffers, etc. The combined load when the unit is in standby must draw power from, but not overload, the USB port.

When the unit is powered on, the unit's power supply will enable separate voltage rails to power devices not directly attached to the microcontroller board. This includes relays, motors, contactors, pumps, etc. This power supply will also supply the board between 9 and 12 Volts DC to the power connector on the arduino board. The power supply may also have other source rails that may or may not be switched with the power state of the unit, but none of these except the 9-12VDC run supply mentioned previously will connect directly to the Arduino board!

What this means is that anything that could load down the Arduino and cause the unit to fail cannot run directly off the board. When line or mains power is lost, the unit should survive in standby mode and operate off a USB battery pack or attached cell phone for at least a couple hours before losing standby power. This feature will allow for blackouts, brownouts, and such so the unit will go right back to work when and if power is restored without losing its wits and memory.

[buffalobillpatrick]

jeff5may: "power is restored without losing its wits and memory"

Thats how they work without a battery.