You'd need a dipole resonant at 2.4GHz on the inside, coax feed via a grommet to a second dipole on the outside. This could certainly improve matters but the attenuation would still be high and the link may still not be reliable. Has anyone published design information and shown test results?
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iSpindels
- Thread starter gingerneil
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OK, sounds to me like someone who perhaps didn't know what they were doing hit on a method that worked, which is not at all unusual. The inner conductor of the coax would not do anything but the outer conductor would act as a probe antenna on the inside of the fermenter and the length outside would function as a second antenna with the lid acting as a ground plane. The length inside and outside should be 1/4 wavelength at 2.4Ghz wich is only 31mm, so quite practical. A piece of rod or wire could equally be used instead of coax but it must go through an electrically insulating grommet or seal. (assuming I'm right which is of course not guaranteed).
The chances of this kind of arrangement working would be greatly improved by having a wifi extender close to the fermenter.
I still think that it would be a bit of a gamble whether or not this could be made to work reliably, and testing is the only way to prove the idea, but it could work.
The chances of this kind of arrangement working would be greatly improved by having a wifi extender close to the fermenter.
I still think that it would be a bit of a gamble whether or not this could be made to work reliably, and testing is the only way to prove the idea, but it could work.
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A thought wich occurred to me would be to find a local amateur radio group. They are usually a mix of professional and amateur radio engineers but a love of beer seems to be universal. They most likely would have the antenna knowledge & the equipment to do the necessary tests and bribed with a suitable quantity of brew would most likely come up with a good solution to this problem if one exists.
The trouble with working with RF is that proper test gear is needed otherwise it's like working in the dark. All ok if something works but if it doesn't then the reason why needs test gear to investigate.
As I say just a thought.
The trouble with working with RF is that proper test gear is needed otherwise it's like working in the dark. All ok if something works but if it doesn't then the reason why needs test gear to investigate.
As I say just a thought.
All it needs is someone to try. Either it helps or it doesn't. WiFi signal strength can be checked with a mobile phone. The iSpindel transmits continuously when in config mode. But I don't have a length of coax handy or a s/s pot I'm willing to drill!
Might try next week with my all-in-one brewer but that has a glass lid and I need to order some coax................
Might try next week with my all-in-one brewer but that has a glass lid and I need to order some coax................
parpot
Regular.
Many thanks for your concise response!
parpot
Regular.
Many thanks for all your responses but I think I shall just carry on with the Hydrometer, it seems easier!
no problem and I quite agree
Nevertheless it's an interesting problem for a nurdy engineer to get to grips with and a solution might be useful for other SS fermenter fans on the forum. (I think my beer improved dramatically when I got rid of my nasty scratched old plastic fermenter)
I have a friend who was the top man for antenna design at the electronics research company I used to work at. I'll drop him a line and see what he thinks. Getting the design & dimensions correct for the probe antenna will improve the link considerably. As pointed out by Kelper & what I had forgotten is that there is some built in reporting of signal strength on a lot of wifi kit & phone apps also give a useful independent indication of wifi signal strength too. The issue really is that the probe antenna needs to be as good as it can be for this to work well. Design optimisation requires other expensive test gear to measure properly, but if the antenna is theoretically correct only marginal improvement is likely via in depth testing.
If I find out anything more useful regarding a good candidate design then I'll post again.
If anyone of a technical bent should want to take this further then the following notes from my antenna expert contact may be of help. He writes:
I assume that the SG reporting device floats on top of the liquid so that its antenna is high and dry. Its antenna will be radiating into a closed cavity, with one wall made of effectively impure water (sorry !) [That's the last invite to my home brew parties he's getting!]. At 2.4 GHz the water will be fairly lossy (think microwave oven principles), so I am guessing that any cavity resonances will be considerably damped. Nevertheless, there will be RF fields set up within it.
The bung aperture at the top ( assuming it's wider than the wall/boss thickness ) will be pretty effective as an antenna due to it interrupting the current that would otherwise flow on the inside of the metal. So I suspect it will radiate outwards with a weakly directional pattern upwards.
If you can position a WiFi access point (AP) fairly closely above the vessel, I think you would stand a good chance of getting enough signal.to operate reliably. I'm talking here about an AP with a wired ethernet connection. Only an experiment would tell you conclusively
Alternatively, you could use a WiFi repeater, i.e. RF to RF like a BT "disc". Normally you place these about halfway between your router and your device, to get roughly equal path loss for the two "hops" of the link. In the brewing case, to overcome the extra loss of the vessel I'd suggest the repeater was much closer to the vessel end.
If you do want to go down the "back to back" antenna route, then as you suggest, a pair of quarter-wave rods linked via an insulating bung would be the right way to go. The base impedance in theory is 35 ohms, so the "coax" in between should be the same impedance. However, since it's so electrically short I wouldn't fuss too much, a hole 2 or 3 times the diameter of the pin would be fine. Silicone rubber isn't too lossy if you want a pressure seal.
One last possibility is to get an AP with a detachable antenna(s). One could then take off the antenna and use coax to a bulkhead mounted quarter-wave antenna probe poking into the vessel. An O-ring sealed SMA with a wire attached suggests itself. Bear in mind that APs often use "reversed sex" SMAs, so you'd need the right sort of plug on the coax at the AP end. Using two antennas gives diversity, which would help avoid the unlucky situation of your single antenna just happening to be at a point of low field.
You could use "WiFi Analyzer" App on an Android phone (for example), which gives a quasi spectrum analyser display of signal strength for each channel. It's fairly slow responding, but gives a good guide to strength and also tells you if there are any competing devices on the same channel (neighbour's smart printer etc etc).
Regarding his last point about the Wifi Analyser app, it occurs to me that a battery powered device will be transmitting data quite infrequently to preserve battery lifetime. The phone app may not therefore be able to reliably detect it (just something to bear in mind).
.... or as Parpot says, just use a hydrometer, you know it makes sense Chhers
I assume that the SG reporting device floats on top of the liquid so that its antenna is high and dry. Its antenna will be radiating into a closed cavity, with one wall made of effectively impure water (sorry !) [That's the last invite to my home brew parties he's getting!]. At 2.4 GHz the water will be fairly lossy (think microwave oven principles), so I am guessing that any cavity resonances will be considerably damped. Nevertheless, there will be RF fields set up within it.
The bung aperture at the top ( assuming it's wider than the wall/boss thickness ) will be pretty effective as an antenna due to it interrupting the current that would otherwise flow on the inside of the metal. So I suspect it will radiate outwards with a weakly directional pattern upwards.
If you can position a WiFi access point (AP) fairly closely above the vessel, I think you would stand a good chance of getting enough signal.to operate reliably. I'm talking here about an AP with a wired ethernet connection. Only an experiment would tell you conclusively
Alternatively, you could use a WiFi repeater, i.e. RF to RF like a BT "disc". Normally you place these about halfway between your router and your device, to get roughly equal path loss for the two "hops" of the link. In the brewing case, to overcome the extra loss of the vessel I'd suggest the repeater was much closer to the vessel end.
If you do want to go down the "back to back" antenna route, then as you suggest, a pair of quarter-wave rods linked via an insulating bung would be the right way to go. The base impedance in theory is 35 ohms, so the "coax" in between should be the same impedance. However, since it's so electrically short I wouldn't fuss too much, a hole 2 or 3 times the diameter of the pin would be fine. Silicone rubber isn't too lossy if you want a pressure seal.
One last possibility is to get an AP with a detachable antenna(s). One could then take off the antenna and use coax to a bulkhead mounted quarter-wave antenna probe poking into the vessel. An O-ring sealed SMA with a wire attached suggests itself. Bear in mind that APs often use "reversed sex" SMAs, so you'd need the right sort of plug on the coax at the AP end. Using two antennas gives diversity, which would help avoid the unlucky situation of your single antenna just happening to be at a point of low field.
You could use "WiFi Analyzer" App on an Android phone (for example), which gives a quasi spectrum analyser display of signal strength for each channel. It's fairly slow responding, but gives a good guide to strength and also tells you if there are any competing devices on the same channel (neighbour's smart printer etc etc).
Regarding his last point about the Wifi Analyser app, it occurs to me that a battery powered device will be transmitting data quite infrequently to preserve battery lifetime. The phone app may not therefore be able to reliably detect it (just something to bear in mind).
.... or as Parpot says, just use a hydrometer, you know it makes sense Chhers
80/-
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If you fancy getting one, then go for it.
I have an ispindel that sits inside my brewtech stainless steel fermenter, inside a fermentation fridge and it connects to the wifi extender I have in the shed with no issues.
I think you will need the extender though, based on my experience.
Seems to me that is the required proof.
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Still available, but price reduced to £36 delivered. Now building using only genuine Lolin wemos control boards as the clone versions are getting increasingly unreliable!
Message if you're interested.
Message if you're interested.
paul3944
Well-Known Member
Haven’t read the whole thread. But do these come with a battery?
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Silly question but is it easy to remove the battery to recharge? I have the appropriate charger so not an issue but I'm guessing an 18650 would last a while on 1 charge in one of these.
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Yes, but you don't need to. It's got a fully protected charging circuit that uses a standard micro USB. If you do want to remove the battery, it's easy to slide the board out of the tube and remove the battery from the standard holder.
lupinehorror
Landlord.
manual and more can be got here
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Also take a look on youtube there's a load of videos on set up and usage.
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