iSpindel - digital WiFi hydrometer

[Harry Bloomfield]

I, too, though static IPs might stop all my gadgets losing their internet connection but I don't use them today as it did not eliminate the problem. I guess the DHCP server in the router is clever enough to avoid the problem unless the firmware is buggy. My phone (Android) never has a problem, but our laptops (Windows) often fail to connect. When rebooting the laptop does not work I reboot the router and range extender and that does always fix it. I think it is a Microsoft issue.

I also often suffered like that, my W10 laptop would sometimes come out of hibernation, listing my AP, but with zero signal strength and refusing to connect to it. The only way to get it to connect was to do a complete restart of W10. SWMBO had similar issues with her laptop. Very annoying.

Giving them a fixed IP has cured that issue, but now it sometimes prefers to connect to my main router, which is weaker/ more distant, than my nearer ones wifi - both have the same SSID and password. Switching 'Flight Mode' off, then straight back on sorts this.

My wired IP cam before, used to display on my laptop at a reported frame rate of 3 to 6 FPS, prior to my giving everything static IP's - the cam always has had a static IP. Since setting everything up with static IP's, it is now reporting 20 to 30 FPS - actual rate depends on the frames content and what changes between frames. Why this has improved so much, I don't understand.

 

[kelper]

Have you set a long lease time in your router's settings?

 

[UKSkydiver]

If I remember correctly from my Microsoft MCSE TCP/IP networking course work, a DHCP server will try to contact the client and reassign the IP address at 1/2 and 7/8ths of the lease length. If it can't reconnect, it will release the IP back to the pool.

So it is possible that the ispindel is offline at that point, but in theory the DHCP server would just assign a new address, unless the pool has run out, which is unlikely unless you have reduced your pool size.

*this is all from a long time ago so I may have not remembered it with 100% accuracy, in which case someone will no doubt assist with thw detail.

 

[UKSkydiver]

just change the 'x' to 'tilt'

Right-click in the chart and select 'series' and then 'SG' scroll down to the trendline settings.

I set it to linear, but you can set it to polynomial and try changing 'polynomial order'

Changing to 3 degree polynomial (and please don't think I understand what I'm typing here) I get:

0.94 + 3.12E-03x + -3.27E-05x^2 + 2.49E-07x^3

And should I change all of the 'x's to *tilt and also remove the spaces (as per the other instructions I've read)

so:

0.94+3.12E-03*tilt+-3.27E-05*tilt^2+2.49E-07*tilt^3

And can you explain what is going on in simple layman's terms? e.g. why is this formula different from the one generated from the ispindel configuration web page?

Cheers

 

[kelper]

The formula given on the iSpindel config is just an example. Hence ex at the beginning. I don't think the spaces matter.

Yes, change all the x's to *tilt

 

[UKSkydiver]

The formula given on the iSpindel config is just an example.

No - what I mean is; using my actual data, why is their 3 deg poly 115 characters and yours is 51?

 

[kelper]

Mine is 103.

But mine has a silly number of decimal places! I could shorten it from

2.4950708612059392E-6*tilt^3 -3.597130446990714E-4*tilt^2 +0.018498247948015193*tilt +0.694611987372000

to

2.49E-6*tilt^3 -3.59E-4*tilt^2 +0.018*tilt +0.69 with neglible loss of accuracy.

You will remember from school formulas like y = x² + 3x ? or A = 4B +2C ? This is what the little x is.

But to enter it in the config it has to be *tilt (which stands for 'times tilt' * is used for multiply and / is used for divide.

 

[UKSkydiver]

Mine is 103.

OK - but if you put your data in their config tool (here: iSpindel Calibration) I suspect it won't come out to the same formula or length - so how have you derived your calcs in your spreadsheet? (I'm not challenging, I'm just interested to know the difference between their calc tool and yours)

 

[UKSkydiver]

And I have two more problems now:

- It doesn't record any temps
- when I short the reset pins out 3-4-5 times, it does not go into local AP / config mode, so I can't input the new formula

May be time for beer.

 

[UKSkydiver]

You will remember from school formulas like y = x² + 3x ? or A = 4B +2C ? This is what the little x is.

But to enter it in the config it has to be *tilt (which stands for 'times tilt' * is used for multiply and / is used for divide.

This bit I know...

But mine has a silly number of decimal places! I could shorten it ... with neglible loss of accuracy.

...But this is the bit I was unsure of. I didn't know you could lose a few decimal points. So I could just have removed a few from each of the calcs and still get a reasonable reading.

Sorry - next question....

Take
2.4950708612059392E-6*tilt^3
and
2.49E-6*tilt^3

I see that you have kept the E from the end of the decimal places where it is followed by a '-' . What is the significance of the E-?

Why not just have 2.49-6*tilt^3

Thank you.

 

[kelper]

My spreadsheet looks at all the data and does some clever calculations to find an approximate formula when it draws a trendline. But you have to tell it whether the relationship is linear, exponential or other. As your data produces a fairly straight line, the formula is quite short. My data produced a 's' shaped curve and needs a more complex formula.

I put my data into the iSpindel config tool and got this

The third-order formula is

0.7412505735876012 + 0.015931077725261908 *tilt-0.0003139332518211446 *tilt*tilt + 0.000002229551006076204 *tilt*tilt*tilt

actually fairly similar. It includes spaces!

tilt*tilt*tilt is equivalent to tilt^3

 

[ChrisT]

I see that you have kept the E from the end of the decimal places (where it is followed by a '-' . What is the significance of the E-?

Why not just have 2.49-6*tilt^3

Thank you.

The E is power of 10, so 10 is 1E2 and 0.01 is 1E-2, so you could remove all of your leading zeros using this.

Chris

 

[kelper]

E is short for expontial. 100 is 10 x 10; 1000 is 10x 10 x 10; 10,000 is 10 x 10 x10 x10 so we count the number of tens

3.2E4 means 3.2 x 10,000 = 32,000

0.0001 can be written as 1 x 10¯⁴ or 1E-4

I hope I'm not confusing you!

It's done to save space, especially on calculators.

If you try and display 0.0000000123456789 on a calculator that only shows nine digits, you see only 0.00000001 losing all the accuracy.

But you can express the number as 1.2345E-9 which is far more accurate.

 

[UKSkydiver]

E is short for expontial. 100 is 10 x 10; 1000 is 10x 10 x 10; 10,000 is 10 x 10 x10 x10 so we count the number of tens

3.2E4 means 3.2 x 10,000 = 32,000

0.0001 can be written as 1 x 10¯⁴ or 1E-4

I hope I'm not confusing you!

It's done to save space, especially on calculators.

If you try and display 0.0000000123456789 on a calculator that only shows nine digits, you see only 0.00000001 losing all the accuracy.

But you can express the number as 1.2345E-9 which is far more accurate.

Thank you (both) that was very well explained, and I'm not great with maths, the point being, that is it very relevant to the formula

 

[Harry Bloomfield]

Have you set a long lease time in your router's settings?

My router suggest that by default, it allows a 12 hour lease.

 

[kelper]

My router suggest that by default, it allows a 12 hour lease.

I set mine to the max of 21 days (on a BT hub)

 

[Harry Bloomfield]

If I remember correctly from my Microsoft MCSE TCP/IP networking course work, a DHCP server will try to contact the client and reassign the IP address at 1/2 and 7/8ths of the lease length. If it can't reconnect, it will release the IP back to the pool.

That makes a lot of sense, compared to what I am seeing in the flesh. I think I said - I have never seen the iSpindel appear in my routers log, never see it in the list of connected devices, never succeeded in pinging its IP. So far as my router is concerned, my iSpindel does not exist, apart from when it attempts to connect through my router.

I have a quite congested LAN with 25 to 30 devices trying to intermittently connect, via two/ at times four routers.

I have just set my router to a lease time of 'infinite' for the main items on my LAN, including the iSpindel.

 

[kelper]

It's the client that contacts the server. https://www.techwalla.com/articles/what-is-dhcp-lease-time

 

[UKSkydiver]

It's the client that contacts the server.

Yeah, I looked it up and found this. I was about to correct myself but you beat me to it.
Not bad for a ~20 year old recollection.

 

[kelper]

apart from it being arse about ***