Bluetooth or Other Remote Control Link

A friend has asked me for help with an idea he has which requires a simple RF link to control a 12 volt circuit. One end of the link would need an MCU to collect the inputs and make a decision about the state of the 12 volt circuit. The RF link is used to control the 12 volt circuit. The MCU end would be battery powered and so needs to be low energy. It is only on with a very low duty cycle, less than a dozen times a day for a short while each time. There may be a need for a bidirectional link to verify the serial number of the remote unit, I'm not sure. The range is single digit feet, but there may be metal in the way, similar to a unit under a car hood for example.

I was originally thinking of using Bluetooth, BLE specifically. But I have had some awkwardness with the connection in various uses. One advantage is that qualified modules are available which get around the FCC certification I believe. I found the NRF51822 Eval Kit which seems to be a SOC with both Bluetooth and an ARM CM0, not bad but no certs I would assume.

If the remote unit does not need to be identified, I would think there are much simpler solutions. I expect the type of xmit and receive modules used in weather stations might be adequate.

Any recommendations for units to consider for a prototype?

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Rick
Reply to
rickman
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Rick

Take a look at the CY8CKIT-042-BLE Bluetooth® Low Energy (BLE) Pioneer Kit from Cypress

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Also comes with Windows/iOS/Android support examples

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Reply to
antedeluvian

I'm dubious about bluetooth working reliably in an environment like that, but you could try.

Car alarm remotes? If you're just triggering a relay or something, you should be ok with a very low bit rate compared with BLE.

There's all kinds of other RF stuff on Sparkfun:

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Reply to
Paul Rubin

Den onsdag den 11. februar 2015 kl. 17.40.32 UTC+1 skrev rickman:

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-Lasse

Reply to
langwadt

A garage opener?

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-TV
Reply to
Tauno Voipio

Is ZigBee still a viable contender for this sort of stuff?

If it's really under hood, it sounds like (a) a difficult EMI environment, and (b) a "whyinhell not just use wired" environment. But I'm sure he has constraints you haven't mentioned.

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Tim Wescott 
Wescott Design Services 
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Reply to
Tim Wescott

I don't automatically question all requirements. If they ask for wireless, I'll give them wireless. I didn't say this would go in a car. I said there might be some level of shielding from metal similar to being under the hood, lots of metal, but not shielded like a PC case. The distance is short, so a bit of attenuation from a loose case shouldn't be a problem.

I don't know much about ZigBee. I believe it is a lower data rate than Bluetooth which would be fine. The one end needs to be low power and I think Zigbee fits that. I'll do a little digging. But I think that is what BLE is in response to, so there may not be much difference.

One nice thing about Bluetooth is there are a million ways to prototype and canned modules with certs are available.

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Rick
Reply to
rickman

Maybe, or a remote engine starter. Are these things on a frequency that is not licensed? I seem to recall that garage door openers are on a frequency that is shared with emergency services. Maybe not a problem at a close range.

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Rick
Reply to
rickman

I don't automatically question _all_ requirements. But I don't see any point in taking a bunch of someone's money to go down a blind ally, either.

You know who you're dealing with.

I know that there are _some_ canned ZigBee modules, but I don't know how much.

I was really just throwing the name out to give you something to research

-- I know that ZigBee was hot several years ago, but I don't know if it's faded from the market or not. If this BLE thing has taken over the ZigBee ecological niche, then it's the way to go.

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Reply to
Tim Wescott

Actually I am thinking it might be better in most respects to use something more like a car fob remote circuit if that can be found in precertified modules. I expect it can't since car fobs are very high volume and I expect every one is a custom design. I'll look up the frequency so at least I have an idea what the regs are. Maybe no certs are needed other than the usual EMI stuff like PCs.

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Rick
Reply to
rickman

You may be right about the simpler transmitter. I'm almost certain that you need more certification if you're an intentional emitter vs. unintentional (like a PC), but I don't know how much.

I suspect that much of the required certification isn't with the FCC, but with the BlueTooth consortium or ZigBee or whoever, who want to make sure you're playing nice with their intellectual property before they give the nod on using their logo on your product.

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Tim Wescott 
Wescott Design Services 
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Reply to
Tim Wescott

an Bluetooth which would be fine.

ZigBee is based on 802.15.4. Standard rate is 256Kb/s. Custom rate upto 1 Mb/s. Should be more than enough for your app.

l do a little digging.

Yes, you can time multiplex the link to save power, as long as you don't ha ve to follow some standards.

pe and canned modules with certs are available.

Only necessary if you are talking between modules between company A and com pany B.

ow much.

802.15.4 chips are around $3 o $4 each.

rch -- I know that ZigBee was hot several years ago, but I don't know if it 's faded from the market or not. If this BLE thing has taken over the ZigB ee ecological niche, then it's the way to go.

Actually, it's WiFi taking over, if power consumption is not an issue.

with the BlueTooth consortium or ZigBee or whoever, who want to make sure you're playing nice with their intellectual property before they give the n od on using their logo on your product.

Yes, it's a lot simpler if you don't have to worry about logo certification . If you are responsible for both sides of the link, who cares about logos ?

Reply to
edward.ming.lee

I think in this case we don't need no stinkin' logo. I think I'm just going to punt and go with the Bluetooth. I wasn't asked to design a marketable system, I am being asked about a proof of concept. I'll just put something together with an Arduino or whatever that works on the lab bench and then we'll see what they really want. The main reason for going with something like Bluetooth is to avoid any certs issue by using pre-certified modules. For this proof of concept it is just to get there with the minimum effort.

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Rick
Reply to
rickman

This is an observation more than anything else:

If you do a one-off, running in a license-free band, per regs but without formal testing or certification, the FCC is not going to be interested enough in you to even verify that you exist. So you could go ahead and make your 400-ish MHz data link (there's some specific band in there; I can't remember) and have a ball.

But for a one-off it's probably less work to go with BT modules even so.

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Reply to
Tim Wescott

If you are just looking for a quick prototype with point-to-point communication I would use a couple of XBee2 (ZigBee) modules. These are certified and very simple to apply.

Lots of examples and documentation (including my website

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A couple of great books --

Building Wireless Sensor Networks: with ZigBee, XBee, Arduino, and Processing ISBN-13: 978-0596807733 ISBN-10: 0596807732

Making Things Talk Practical Methods for Connecting Physical Objects ISBN: 978-0-596-51051-0 ISBN 10: 0-596-51051-9

(* jcl *)

Reply to
John Luciani

Of course there is also XBEE. I recommend this book to learn about it

"The Hands-on XBEE Lab Manual: Experiments that Teach you XBEE Wirelesss Communications " by Jon Titus

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Reply to
antedeluvian

Would something like this satisfy your requirements? Or do you really need the complexity of WiFi or BlueTooth?

It's basically a paired transmitter and receiver pair for $20, unidirectional.

Frank McKenney

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  is the existence of these great plain limitations which force all 
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Reply to
Frnak McKenney

Thanks, this is interesting.

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Rick
Reply to
rickman

You could look up one of the Xbee RF Modules. You could probably be happy with the basic 802.15.4 modules, without the need for ZigBee support.

Pere

Reply to
o pere o

Check this Xbee alternative solution based on Sub-G band. USART port. This module is available as "Ready-to-use," focuses on ease of integration even for non RF specialists, thus limit technological risks, while reducing the development time and cost. The following is the link for details:

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Reply to
Jason wu

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