I know variations to this have been asked before, but I’m curious if there is any recommendations of how to implement an open sourced, battery operated blind controller. I have the common 2" faux wooden blinds throughout my house (20+ on just my main floor - thanks builder!). The blinds are all recently installed, all the same brand, and easy to implement the mechanical aspect of installing a servo to actuate them - I’ve done so successfully. I could probably do this for <$10/blind, which I find reasonable.
For another few $ per blind, I can include an Arduino and a 2.4MHz radio, which will give me a working solution. Even with the low power hacks to the Arduinos, because the radio can’t sleep, I’ve been told that battery life will be very short due to the power usage of the radios. One alternative would be to have the radios poll the controller for status updates, but this is less than ideal and I have not tried this.
Anyone have ideas on how to control remote electronics capable of driving a servo on battery power with a low overall cost? I’d love to hear any ideas you may have.
It is a big challenge. To have a reasonable response time you need to have the radio always on so it can instantly respond to a command but to have a reasonable battery life you need to sleep the device most of the time (i.e. the polling you refer to).
They are mutually exclusive which is why I think you rarely see battery powered actuators of this type. You can’t sleep most of the time and instantly respond to a command and you can listen all the time and have a reasonable battery life.
I think your best bet will be to see if you can use some really high capacity batteries (e.g. D cell or bigger) to power your device or figure out a way to power them from your mains power or or something like POE which will probably require putting holes in the wall.
I’ve not implemented anything myself but have been thinking about the problem for awhile. As we approach summer having a way to auto raise or lower the blinds and shades could shave a few degrees off of the house temp in the afternoon. But I’ve come to the conclusion that it needs to be wired powered, not battery.
I’ve just got some second hand wireless tags (wirelesstag.net) and each sensor gets a year or more out of a button battery. I suspect their secret is they talk to a powered hub unit that can probably skip much of the wasteful control comms in connecting Wi-Fi.
I started to look into this a while ago and parked up it for a while as I didn’t have time to fully investigate.
Radio receivers sipping power will only be part of the issue running on batteries. The other issue is how long your power supply is able to provide a high enough voltage AND current to turn the motor. e.g. if you need to use a boost converter to get a high enough voltage will it allow enough current to flow to get the motor to turn at the required speed/torque as the battery voltage gets lower.
Just to be clear, I’m not trying to raise and lower blinds, but instead just tilt them up or down. There seems to be very little resistance on the servo when doing this, and it only takes a second to move from closed to open to closed. My less than scientific theory is that I could get at least a month or more of use before battery replacement would be required.
I’m curious how the commercial blinds do this. They have an rf remote, raise and lower a shade and run off of a few AA batteries. Oh, and cost several hundred dollars PER shade.
There has to be another way…
It’ll be a while until I’ll need to worry about this myself, but Google gave me http://flipflic.com/ which looks promising. Crowdfunding it though, so need to see if it pans out
Looked into the wirelesstag sensors. They are pretty cool, but they are transmit only. That is the real key, because they can be set to transmit for a fraction of a second every x seconds. This amounts to a very low power usage. For something that has to receive transmissions, the receiver’s radio must remain in receive mode continuously, or it could miss a transmission. Although receive mode typically uses less power than transmit, from what I understand it will still quickly drain a battery source.
The Bali blinds (I believe that was the brand I saw) does just this - runs off batteries and receives an RF signal to raise/lower the blinds. This tells me there is a way to accomplish this with low power usage, I’m just not sure what this method is.
Ahh fair enough. Though I’m pretty sure the tags can receive, just it may take a few seconds for them to react, which may be too much delay for some people/cases. I can tell them to beep, or turn their light on (those types that have one), but it can take a few seconds.
You make a good point. I overlooked the fact that you can make them beep.
They must poll the hub every so often for status, or maybe I’m wrong and
there’s another way they accomplish this.
Have you looked at something like an RFM69? Those are 433/868/915MHz RF transceivers and have low power/sleep modes.
I’ve used them previously and managed to get decent life out of the batteries by using sleep cycles. In combination with the sending transceiver retrying if the message isn’t acknowledged, the receiving transceiver sleeps for a period and wakes up for a shorter period. The key is that the awake period is timed long enough it covers a retry period so if the radio is asleep on the first transmissions it should be awake for the second transmission.
Is (low) response time really a key requirement for this application? If I understand the concept correctly, the idea is to let openHAB automatically control the blinds (tilt to open/close position), presumably based on information about the weather, or maybe a sensor that measures the light level in the room, or?
In either case, I would suggest that waking up once a minute to check the conditions and decide whether the blinds should be open or closed for the next minute, must be more than good enough.
Or, am I totally missing the point here?
No, your not missing the point at all. That could very well be a viable option, and would not require the receiver to be active 24/7. It would require 1,440 transmits/day to poll openhab for status. I’m not sure from a power usage how much better this is, but I would imagine it would be better than continuously running.
The downside to this is if you wanted to make a manual change, it would not be immediate. It could take up to a minute, or whatever you set your polling period to.
I would be interested in checking this out to see if/how this would work in actuality. I’m currently using nrf24 modules for xcvrs, and would likely test with those.
Did you read my post? If the nrf24s have a sleep mode you could experiment with the duty cycle of the receiving radio rather than polling which would give you a better response time.
I did read it, but haven’t experimented with the radio sleep modes at all yet. I only have a vague understanding of how it works, or even how to implement it. I know it supports it - that’s about it. As I understand, sleep mode doesn’t support wake up from an rf signal. I’ll have to read up more on the capabilities of the nrf24 and rfm69
The idea of duty cycling isn’t to wake on rf signal (that’s an interrupt). The idea is the radio willingly goes to sleep for a set period of time and then wakes up and checks if there are any messages to receive, going back to sleep afterwards.
I’m also working on something very similar but haven’t got far with the radio communication yet. It’s clear that WiFi is not the answer, it has to be 433 MHz type of radio communication. There are definitely precedents for getting this to work.
I’m hoping to solve the battery life issue with a cca 8 x 12 cm solar panel recharging the batteries during the day - since blinds are always in windows. This is more important for my application which is actually raising and lowering the blind and a lot of torque is needed.
I’m not saying this is the way you should implement it (I’m a ‘wired’ guy, myself), but you maybe have heard of the ESP8266. It’s a very, very low-cost microcontroller with integrated Wifi. Basically, it supports deep sleep and so on, and can remain ‘active’ while using very little power. Apparently they can go for a year on a LiPo cell (don’t remember the specs of the cell, though).
I recently bought one just to tinker with the technology (Wifi+microcontroller under 10 Euros (12 Dollars) sounded too good to be true). I’m not sure about battery life, but power draw is REALLY low, Wifi connectivity is fast, reliable and you can even use the Arduino IDE (with some 3rd party libraries) to write code for the device.
Maybe worth looking into, and almost worth buying even if it doesn’t work out for that specific project…
Dont know if you talking about blinds or shutters. With blinds you have daylight all the day, why not using small solarpanel to refill the batteries. With shutters you have to calculate the time for refilling, depending if you close the shutters during the day.
I was hoping to do this on my 2" Faux wood blinds. I have a ton of blinds
throughout my house, so I’d like to keep the cost per blind as low as
possible. Solar panels are doable, but I have yet to figure out the best
method for having the blinds respond to commands. I have not spent any
time on this in several months, but when I come back to it I’ll be sure to
post my results, unless someone beats me to it.
Just a quick thought: Maybe using solar charged power banks would be a solution to your energy problem. Easily buyable at your favorite china dealer. Charging is already implemented, Nice 5V output is also already in there. Finally you got enough juice to actuate the servo.