Domoticz

Spoiler: show

htilburgs wrote:I'm trying to minimalize the dashboard, so no blocktitles and extra's. This is work in progress, but I like to share how it does look right now:

What rainscript are you using? I get a lot of errors with my old rainscript.

I'm using this one....

Spoiler: show

Code: Select all

-- =============================================================================================================
-- IsItGonnaRain( int minutesinfuture)
-- returns: int avarage rainfall for the next minutesinfuture
-- =============================================================================================================
-- Function to get rain prediction from Buienradar.nl (dutch)
-- Original script here: https://www.domoticz.com/wiki/Is_it_gonna_rain
--
-- Written in LUA by Hans van der Heijden (h4nsie @ gmail.com)
-- Spring 2015
-- 28-03-2015 v0.3 bug: quotes around url added.
-- 27-03-2015 v0.2 return value is now average for next time
-- 26-03-2015 v0.1 Initial release
-- todo: some error checking on http and file handling (tmp file)
----------------------------------------------------------------------------------------------------------------
-- Marco van Wijngaarden
-- 30-08-2016 v1.0 Adopted and updated the above scripts
-- 30-08-2016 v1.1 Updated the request URL, apparently buienrader is redirecting to different url
-- 30-08-2016 v1.2 Updated CURL to follow redirect and reverted (back to documented) request URL
--
----------------------------------------------------------------------------------------------------------------
-- Buienradar.nl -- 
---------------------
-- Gratis Weerdata --
--
-- Buienradar stelt gratis weerdata beschikbaar voor particulieren en bedrijven (website/intranet). 
-- Het gebruik van onderstaande weerdata is alleen toegestaan voor niet-commerciële doeleinden. 
-- Het gebruik voor mobiele toepassingen of commerciële doeleinden vereist toestemming van Buienradar, zie ook de Disclaimer.
-- Vraag hier toestemming aan voor het gebruik van de weerdata: http://www.buienradar.nl/overbuienradar/contact 
-- Vragen, suggesties of een leuk idee? Neem contact met ons op en bouw mee aan Buienradar!
-- 
------------------------------------------------------------
-- Buienradar widget - Neerslagdata op basis van coördinaten
------------------------------------------------------------
--
-- Op basis van de door u gewenste coördinaten (latitude en longitude) kunt u de neerslag tot twee uur vooruit ophalen in tekstvorm. 
-- De data wordt iedere 5 minuten geüpdatet. 
-- Op deze pagina kunt u de neerslag in tekst vinden: http://gps.buienradar.nl/getrr.php?lat=51&lon=3
-- De waarde 0 geeft geen neerslag aan (droog), de waarde 255 geeft zware neerslag aan. 
-- Gebruik de volgende formule voor het omrekenen naar de neerslagintensiteit in de eenheid millimeter per uur (mm/u):
-- Neerslagintensiteit = 10^((waarde-109)/32)
-- Ter controle: een waarde van 77 is gelijk aan een neerslagintensiteit van 0,1 mm/u.
--
-- =============================================================================================================
-- config ------------------------------------------------------------------------------------------------------
-- =============================================================================================================
--
-- Set your local position (latitude and longitude)
local latitude                  = 'xx.xx'             -- your home latitude, set as a user variable
local longitude                 = 'x.xx'              -- your home longtitude, set as a user variable
-- timewindow for prediction
local minutesinfuture           = 30                                -- (int) minutes in future to calculate rain
-- threshold for switch (when do we actually call it rain and want to act accordingly)
local switchthreshold           = 70                                -- (int) value to toggle virtual switch
-- Rain switch (ON when rain above threshold, else OFF)
local rainswitchname            = "Regen verwacht"                  -- (str) name for switch to toggle
-- Virtual device (txt) displays textual result
local idxRegenmmUur             = IDX                              -- IDX for virtual (text) sensor
-- Show results in log
local debug                     = 0                                 -- 1 = ON or 0 = OFF
-- NMA notifications (only during the day)
local notify                    = false                             -- (bool) set 'false' or 'true'
-- URL for data request
local requesturl                = "http://gadgets.buienradar.nl/data/raintext" 
-- redirects to "http://gadgets.buienradar.nl/data/raintext"
-- Where do we store the data (tmp) file
local tempfilename              = "/home/pi/domoticz/scripts/tmp/rain.tmp" 
-- default to activate script (set 'false' to run once every 5 minutes or 'true' to run every minute)
local active                    = false                           -- (bool) set 'false' or 'true'
--
-- =============================================================================================================
--
-- No edit required below this line
--
-- =============================================================================================================
--
-- execute (activate) every 5 minutes
local time = os.date("*t")
if ((time.min % 5)==0) then
    -- set to active
    active = true
end
--
-- =============================================================================================================
-- Functions ---------------------------------------------------------------------------------------------------
-- =============================================================================================================

-- function to split a string --
function splitString(str, delim, maxNb)
    -- Eliminate bad cases...
    if string.find(str, delim) == nil then
        return { str }
    end

    if maxNb == nil or maxNb < 1 then
        maxNb = 0    -- No limit
    end

    local result = {}
    local pat = "(.-)" .. delim .. "()"
    local nb = 0
    local lastPos
    for part, pos in string.gmatch(str, pat) do
        nb = nb + 1
        result[nb] = part
        lastPos = pos
        if nb == maxNb then break end
    end
    -- Handle the last field
    if nb ~= maxNb then
        result[nb + 1] = string.sub(str, lastPos)
    end

    return result
end

-- function to request rain data 
function IsItGonnaRain(requesturl,latitude,longitude,tempfilename,minutesinfuture,debug)

    local averagerain = 0
    local totalrain = 0
    local rainlines = 0
    
    -- construct the request URL
    local url = requesturl..'?lat='..latitude..'&lon='..longitude
    
    -- print to log
    if (debug == 1) then print("| Request URL .............. : " .. url) end

    -- now get the data
    local trigger_action = 'curl -Lo '..tempfilename..' "'..url..'"' 
    -- CURL options:    -s for Silent (no error messages)
    --                  -o for Write output to file instead of stdout.
    --                  -L Follow redirects if the server reports that the requested page has moved (indicated with a Location: header and a 3XX response code)
    handle = os.execute(trigger_action)

    -- print request result to log
    if (debug == 1) then
        if handle then
            print("| CURL Data request ........ : Success")
        else
            print("! CURL Data request ........ : Failed")
        end
    end

    -- open file and process data
    file = io.open(tempfilename, "r")

        -- count datalines
        local linenbr = 0
        
        -- now analyse the received lines
        while true do
            line = file:read("*line")
            if not line then break end
            
            -- count received lines
            linenbr = linenbr+1
            
            -- line/data format is like 000|15:30 per line, we need to split the string
            raindata    = splitString(line,"|")
            rain        = tonumber(raindata[1])
            linetime    = raindata[2]

            -- Linetime2 holds the full date calculated from the time on each line
            linetime2   = os.time{year=os.date('%Y'), month=os.date('%m'), day=os.date('%d'), hour=string.sub(linetime,1,2), min=string.sub(linetime,4,5), sec=os.date('%S')}
            -- calculate the time difference between data/line and os time
            difference  = os.difftime (linetime2,os.time())

            -- When a line entry has a time in the future AND is within the given range, then add/totalize the rainfall
            if ((difference >= 0) and (difference <= minutesinfuture*60)) then
                
                -- print (relevant) data to log
                if (debug == 1) then print("| Rain data (line) ......... : " .. line) end
                
                -- calculate totals
                totalrain = totalrain+rain
                rainlines = rainlines+1
            end
        end
    -- close the file
    file:close()
    
    -- Returned value is average rain fall for next (int) minutes
    -- 0 is no rain, 255 is very heavy rain
    -- When needed, mm/h is calculated by 10^((value -109)/32) (example: 77 = 0.1 mm/hour)
    averagerain = totalrain/rainlines
    
    -- print summary to log
    if (debug == 1) then 
        print("| Rain data received # lines : " .. linenbr)
        print("| In timerange # lines ..... : " .. rainlines)
        print("| Total rain ............... : " .. totalrain)
        print("| Average rain calculated .. : " .. averagerain)
    end

    return(averagerain)

end

-- Functions to round a number to the given number of decimal places
-- returns result as string (text)
function round(num, idp)
  return string.format("%." .. (idp or 0) .. "f", num)
end
-- returns result as a number
function round2number(num, idp)
  return tonumber(string.format("%." .. (idp or 0) .. "f", num))
end

-- Note: If the number is rounded in order to be printed (as text) use function "round" (removed the tonumber function)
-- Converting to number then back to string would reintroduce rounding errors, so for numbers use "round2number" function

-- =============================================================================================================
-- Process -----------------------------------------------------------------------------------------------------
-- =============================================================================================================

commandArray = {}
-- start numbering at 1 
indexArray=1

-- executes when active (every 5 minutes)
if (active) then

    -- when debugging set to 1, writing to log starts here
    if (debug == 1) then
        print("+--------------------------------------------------+")
        print("| =============== IS IT GONNA RAIN =============== |")
        print("+--------------------------------------------------+")
    end

    -- rain variables
    local regen = 0
    local regenmmUur = 0
    local rainstr = ""

    -- execute function (for given future minutes)
    regen = IsItGonnaRain(requesturl,latitude,longitude,tempfilename,minutesinfuture,debug)
    
    -- round result
    if (regen > 0) then
        regen = round2number(regen, 0)
    end

    -- convert rain to mm/uur
    if (regen > 0) then
        regenmmUur = 10^((regen-109)/32)
        regenmmUur = round(regenmmUur, 3)
    end

    -- textual result
    if (regen > 0) then
        rainstr = tostring("Regen verwacht: "..regen.." (".. regenmmUur.." mm/uur) binnen "..minutesinfuture.." minuten")
    else
        rainstr = tostring("Geen regen verwacht binnen komende "..minutesinfuture.." minuten")
    end

    -- write value to virtual (text) sensor
    if ((idxRegenmmUur) and (regenmmUur)) then
        commandArray[indexArray] = {['UpdateDevice'] = tostring(idxRegenmmUur)..'|0|'..rainstr}
        indexArray=indexArray+1
    end

    -- when debugging set to 1, write to log
    if (debug == 1) then 
        print("| Rain text ................ : " .. rainstr)
    end

    -- toggle switch ON
    if regen > switchthreshold and otherdevices[rainswitchname]=='Off' then
        
        -- send notification during the day
        if (timeofday['Daytime']) and (notify) then
            commandArray[indexArray] = {['SendNotification']=rainstr}
            indexArray=indexArray+1
        end
        
        -- change switch to ON
        commandArray[indexArray] = {[rainswitchname]='On'}
        indexArray=indexArray+1
    end

    -- toggle switch OFF
    if regen == 0 and otherdevices[rainswitchname] =='On' then
        
        -- send notification during the day
        if (timeofday['Daytime']) and (notify) then
            commandArray[indexArray] = {['SendNotification']=rainstr}
            indexArray=indexArray+1
        end
        
        -- change switch to OFF
        commandArray[indexArray] = {[rainswitchname]='Off'}
        indexArray=indexArray+1
    end

    -- logging end
    if (debug == 1) then
        print("+--------------------------------------------------+")
        print("| --------------------- END ---------------------- |")
        print("+--------------------------------------------------+")
    end

end

return commandArray

htilburgs wrote:I'm using this one....

Spoiler: show

Code: Select all

-- =============================================================================================================
-- IsItGonnaRain( int minutesinfuture)
-- returns: int avarage rainfall for the next minutesinfuture
-- =============================================================================================================
-- Function to get rain prediction from Buienradar.nl (dutch)
-- Original script here: https://www.domoticz.com/wiki/Is_it_gonna_rain
--
-- Written in LUA by Hans van der Heijden (h4nsie @ gmail.com)
-- Spring 2015
-- 28-03-2015 v0.3 bug: quotes around url added.
-- 27-03-2015 v0.2 return value is now average for next time
-- 26-03-2015 v0.1 Initial release
-- todo: some error checking on http and file handling (tmp file)
----------------------------------------------------------------------------------------------------------------
-- Marco van Wijngaarden
-- 30-08-2016 v1.0 Adopted and updated the above scripts
-- 30-08-2016 v1.1 Updated the request URL, apparently buienrader is redirecting to different url
-- 30-08-2016 v1.2 Updated CURL to follow redirect and reverted (back to documented) request URL
--
----------------------------------------------------------------------------------------------------------------
-- Buienradar.nl -- 
---------------------
-- Gratis Weerdata --
--
-- Buienradar stelt gratis weerdata beschikbaar voor particulieren en bedrijven (website/intranet). 
-- Het gebruik van onderstaande weerdata is alleen toegestaan voor niet-commerciële doeleinden. 
-- Het gebruik voor mobiele toepassingen of commerciële doeleinden vereist toestemming van Buienradar, zie ook de Disclaimer.
-- Vraag hier toestemming aan voor het gebruik van de weerdata: http://www.buienradar.nl/overbuienradar/contact 
-- Vragen, suggesties of een leuk idee? Neem contact met ons op en bouw mee aan Buienradar!
-- 
------------------------------------------------------------
-- Buienradar widget - Neerslagdata op basis van coördinaten
------------------------------------------------------------
--
-- Op basis van de door u gewenste coördinaten (latitude en longitude) kunt u de neerslag tot twee uur vooruit ophalen in tekstvorm. 
-- De data wordt iedere 5 minuten geüpdatet. 
-- Op deze pagina kunt u de neerslag in tekst vinden: http://gps.buienradar.nl/getrr.php?lat=51&lon=3
-- De waarde 0 geeft geen neerslag aan (droog), de waarde 255 geeft zware neerslag aan. 
-- Gebruik de volgende formule voor het omrekenen naar de neerslagintensiteit in de eenheid millimeter per uur (mm/u):
-- Neerslagintensiteit = 10^((waarde-109)/32)
-- Ter controle: een waarde van 77 is gelijk aan een neerslagintensiteit van 0,1 mm/u.
--
-- =============================================================================================================
-- config ------------------------------------------------------------------------------------------------------
-- =============================================================================================================
--
-- Set your local position (latitude and longitude)
local latitude                  = 'xx.xx'             -- your home latitude, set as a user variable
local longitude                 = 'x.xx'              -- your home longtitude, set as a user variable
-- timewindow for prediction
local minutesinfuture           = 30                                -- (int) minutes in future to calculate rain
-- threshold for switch (when do we actually call it rain and want to act accordingly)
local switchthreshold           = 70                                -- (int) value to toggle virtual switch
-- Rain switch (ON when rain above threshold, else OFF)
local rainswitchname            = "Regen verwacht"                  -- (str) name for switch to toggle
-- Virtual device (txt) displays textual result
local idxRegenmmUur             = IDX                              -- IDX for virtual (text) sensor
-- Show results in log
local debug                     = 0                                 -- 1 = ON or 0 = OFF
-- NMA notifications (only during the day)
local notify                    = false                             -- (bool) set 'false' or 'true'
-- URL for data request
local requesturl                = "http://gadgets.buienradar.nl/data/raintext" 
-- redirects to "http://gadgets.buienradar.nl/data/raintext"
-- Where do we store the data (tmp) file
local tempfilename              = "/home/pi/domoticz/scripts/tmp/rain.tmp" 
-- default to activate script (set 'false' to run once every 5 minutes or 'true' to run every minute)
local active                    = false                           -- (bool) set 'false' or 'true'
--
-- =============================================================================================================
--
-- No edit required below this line
--
-- =============================================================================================================
--
-- execute (activate) every 5 minutes
local time = os.date("*t")
if ((time.min % 5)==0) then
    -- set to active
    active = true
end
--
-- =============================================================================================================
-- Functions ---------------------------------------------------------------------------------------------------
-- =============================================================================================================

-- function to split a string --
function splitString(str, delim, maxNb)
    -- Eliminate bad cases...
    if string.find(str, delim) == nil then
        return { str }
    end

    if maxNb == nil or maxNb < 1 then
        maxNb = 0    -- No limit
    end

    local result = {}
    local pat = "(.-)" .. delim .. "()"
    local nb = 0
    local lastPos
    for part, pos in string.gmatch(str, pat) do
        nb = nb + 1
        result[nb] = part
        lastPos = pos
        if nb == maxNb then break end
    end
    -- Handle the last field
    if nb ~= maxNb then
        result[nb + 1] = string.sub(str, lastPos)
    end

    return result
end

-- function to request rain data 
function IsItGonnaRain(requesturl,latitude,longitude,tempfilename,minutesinfuture,debug)

    local averagerain = 0
    local totalrain = 0
    local rainlines = 0
    
    -- construct the request URL
    local url = requesturl..'?lat='..latitude..'&lon='..longitude
    
    -- print to log
    if (debug == 1) then print("| Request URL .............. : " .. url) end

    -- now get the data
    local trigger_action = 'curl -Lo '..tempfilename..' "'..url..'"' 
    -- CURL options:    -s for Silent (no error messages)
    --                  -o for Write output to file instead of stdout.
    --                  -L Follow redirects if the server reports that the requested page has moved (indicated with a Location: header and a 3XX response code)
    handle = os.execute(trigger_action)

    -- print request result to log
    if (debug == 1) then
        if handle then
            print("| CURL Data request ........ : Success")
        else
            print("! CURL Data request ........ : Failed")
        end
    end

    -- open file and process data
    file = io.open(tempfilename, "r")

        -- count datalines
        local linenbr = 0
        
        -- now analyse the received lines
        while true do
            line = file:read("*line")
            if not line then break end
            
            -- count received lines
            linenbr = linenbr+1
            
            -- line/data format is like 000|15:30 per line, we need to split the string
            raindata    = splitString(line,"|")
            rain        = tonumber(raindata[1])
            linetime    = raindata[2]

            -- Linetime2 holds the full date calculated from the time on each line
            linetime2   = os.time{year=os.date('%Y'), month=os.date('%m'), day=os.date('%d'), hour=string.sub(linetime,1,2), min=string.sub(linetime,4,5), sec=os.date('%S')}
            -- calculate the time difference between data/line and os time
            difference  = os.difftime (linetime2,os.time())

            -- When a line entry has a time in the future AND is within the given range, then add/totalize the rainfall
            if ((difference >= 0) and (difference <= minutesinfuture*60)) then
                
                -- print (relevant) data to log
                if (debug == 1) then print("| Rain data (line) ......... : " .. line) end
                
                -- calculate totals
                totalrain = totalrain+rain
                rainlines = rainlines+1
            end
        end
    -- close the file
    file:close()
    
    -- Returned value is average rain fall for next (int) minutes
    -- 0 is no rain, 255 is very heavy rain
    -- When needed, mm/h is calculated by 10^((value -109)/32) (example: 77 = 0.1 mm/hour)
    averagerain = totalrain/rainlines
    
    -- print summary to log
    if (debug == 1) then 
        print("| Rain data received # lines : " .. linenbr)
        print("| In timerange # lines ..... : " .. rainlines)
        print("| Total rain ............... : " .. totalrain)
        print("| Average rain calculated .. : " .. averagerain)
    end

    return(averagerain)

end

-- Functions to round a number to the given number of decimal places
-- returns result as string (text)
function round(num, idp)
  return string.format("%." .. (idp or 0) .. "f", num)
end
-- returns result as a number
function round2number(num, idp)
  return tonumber(string.format("%." .. (idp or 0) .. "f", num))
end

-- Note: If the number is rounded in order to be printed (as text) use function "round" (removed the tonumber function)
-- Converting to number then back to string would reintroduce rounding errors, so for numbers use "round2number" function

-- =============================================================================================================
-- Process -----------------------------------------------------------------------------------------------------
-- =============================================================================================================

commandArray = {}
-- start numbering at 1 
indexArray=1

-- executes when active (every 5 minutes)
if (active) then

    -- when debugging set to 1, writing to log starts here
    if (debug == 1) then
        print("+--------------------------------------------------+")
        print("| =============== IS IT GONNA RAIN =============== |")
        print("+--------------------------------------------------+")
    end

    -- rain variables
    local regen = 0
    local regenmmUur = 0
    local rainstr = ""

    -- execute function (for given future minutes)
    regen = IsItGonnaRain(requesturl,latitude,longitude,tempfilename,minutesinfuture,debug)
    
    -- round result
    if (regen > 0) then
        regen = round2number(regen, 0)
    end

    -- convert rain to mm/uur
    if (regen > 0) then
        regenmmUur = 10^((regen-109)/32)
        regenmmUur = round(regenmmUur, 3)
    end

    -- textual result
    if (regen > 0) then
        rainstr = tostring("Regen verwacht: "..regen.." (".. regenmmUur.." mm/uur) binnen "..minutesinfuture.." minuten")
    else
        rainstr = tostring("Geen regen verwacht binnen komende "..minutesinfuture.." minuten")
    end

    -- write value to virtual (text) sensor
    if ((idxRegenmmUur) and (regenmmUur)) then
        commandArray[indexArray] = {['UpdateDevice'] = tostring(idxRegenmmUur)..'|0|'..rainstr}
        indexArray=indexArray+1
    end

    -- when debugging set to 1, write to log
    if (debug == 1) then 
        print("| Rain text ................ : " .. rainstr)
    end

    -- toggle switch ON
    if regen > switchthreshold and otherdevices[rainswitchname]=='Off' then
        
        -- send notification during the day
        if (timeofday['Daytime']) and (notify) then
            commandArray[indexArray] = {['SendNotification']=rainstr}
            indexArray=indexArray+1
        end
        
        -- change switch to ON
        commandArray[indexArray] = {[rainswitchname]='On'}
        indexArray=indexArray+1
    end

    -- toggle switch OFF
    if regen == 0 and otherdevices[rainswitchname] =='On' then
        
        -- send notification during the day
        if (timeofday['Daytime']) and (notify) then
            commandArray[indexArray] = {['SendNotification']=rainstr}
            indexArray=indexArray+1
        end
        
        -- change switch to OFF
        commandArray[indexArray] = {[rainswitchname]='Off'}
        indexArray=indexArray+1
    end

    -- logging end
    if (debug == 1) then
        print("+--------------------------------------------------+")
        print("| --------------------- END ---------------------- |")
        print("+--------------------------------------------------+")
    end

end

return commandArray

Thx. Running fine now. Removed the switch part, because I don't need it.

Does someone know how to remove the ": 30%" after a title

Maybe by just renaming it

blocks[xx] = {};
blocks[xx]['title'] = 'Slaapkamer'';

where xx is your IDX?

I found no way.... It's in the main.js (line 1040) Maybe overrule with custom.js?

htilburgs wrote:I found no way.... It's in the main.js (line 1040)

Code: Select all

html+='<strong class="title">'+device['Name']+': '+device['Level']+'%'+'</strong>';

Maybe overrule with custom.js?

Maybe blocks[IDX]['level'] = false; is an option to add.
Just opened GitHub issue for this.

My layout right now still have to add a lot of switches and scenes but the tiny buttons to control the radio bother me does anyone know how to change that?
(We added some lights from the neighbors as our RFXCom receiver/transmitter detected them)
(Thuis with 'ss' was for debugging purposes because I thought nothing was changing when I uploaded CONFIG.js )

Trying to minimalize my sliders view.
Only the line of Salontafel is thicker than the rest. Maybe someone knows how to get it smaller or a better way to handle this?

@hansienl, curious, how did you get rid of the %??

htilburgs wrote:@hansienl, curious, how did you get rid of the %??

Short of memory? You told me before. I edited the main.js.

Ah, ok... Think it's the weather.
I don't like to edit main.js, it make it hard to update.
I hoped that the block[idx]['level']=false; came through (Tried it, but no luck)

htilburgs wrote:Ah, ok... Think it's the weather.
I don't like to edit main.js, it make it hard to update.
I hoped that the block[idx]['level']=false; came through (Tried it, but no luck)

I just bought him another beer. Maybe that speed up things?

I liked your idea, but with a little different buttons and moved the slider further down.
(And I don't have a problem with different thickness).

HansieNL wrote:

htilburgs wrote:Ah, ok... Think it's the weather.
I don't like to edit main.js, it make it hard to update.
I hoped that the block[idx]['level']=false; came through (Tried it, but no luck)

I just bought him another beer. Maybe that speed up things?

Hold on, let me fix it
(thanks!)

Check latest beta!

robgeerts wrote:Check latest beta!

Spoiler: show

Code: Select all

blocks[295] = {}
blocks[295]['hide_data'] = true;

Thanks... works like a charm. Another Github issue can be closed.

Finally managed to finish my custom wall mounting for the 10" tablet.
Just used a spruce plank and stained it to get this brownish color.
Also i've bought four round magnets with a hole in the middle to attach the tablet to them, this is the next part of the project, will start this within the next days.
Since the magnets are made of metal, they transmit energy and i've attached a wire to each of them to realize the loading process. I've never thought this would actually work, but why not, easy physics.

Here are some photos of the current project status:





If you are wondering about the second picture, i soldered the wire not directly to the magnet because it would lose its magnetism when heated over 80° C so i've soldered it to a washer and placed the magnet on top.

Project cost currently around 13€ (1€ wood, 6€ magnets, 20ct screws, 5€ usb cable). Think will finish it with not more than 20€.

How to connect your tablet to the magnets? And how to transfer the energy from the magnets to the the tablet battery?

There are two other magnets which will be attached to the tablet itself. How i will do it in fact will be the other question
Then simply two wires which are going to a small micro usb plug which is plugged into the tablet. Worked quite good while testing, but i've not yet decided how to mount the magnets to the back of the tablet.