VW Beetle Choke Delay

adds a 2 minute extension to the legth of time the choke stays on on 75 VW Beetle on cold mornings

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my daughters '75 VW Superbug L is missing its thermostat and on cold mornings (around 0deg C) the choke opens before the engine has had a chance to warm up. I intend on making an electronic thermostat for it but in the mean time it was easier to make a circuit to cut power to the choke for a couple of minutes on a cold morning to extend the time it stays closed for.

Nothing Fancy about this one.

Uses an Arduino UNO clone (more on that later) to read a one wire temp sensor and drive a relay to disconnectpower from the choke heater element for a couple of minutes on cold mornings.

The Craburettor in the VW Beetle has an Automatic choke which is activated by a temperature senstive spring. The spring when cold closes the choke and as it warms up slowly opens the choke, when all things are working at the same rate as the engine warms up. The spring is heated by small heater element. there is a small amount of adjustment to compensate between summer and winter but With a missing thermostat the old beetle takes abit longer to warm up than the choke adjustment will allow.

This circuit will connect between the choke and its power supply. this will provide power to drive the UNO. The idea is to make the instalation as simple as possible as Ill have to post it to my daughter for her to fit up.

Should be as simple as disconnect the spade connector on the choke and plug it into this device plug a flying lead from this to the choke terminal and attach a wire to a suitable ground and cable tie the temperature sensor to the intake manifold.

ino - 3.70 kB - 07/06/2016 at 08:23


  • It was a good idea but.....

    Saabman08/21/2016 at 10:39 0 comments

    while working on this I wanted to get an idea as to how long I should set the time delay I got my daughter to give the system a manual test getting her to disconnect the choke supply voltage and driving for a couple of minutes then pulling over and hooking up the choke supply than continuing to drive - what we found is that it didn't really make any noticeable difference. I've decided the project isntbgoingbto help in its current form. I'm thinking of reworking things and just making a data logger and making recording some temperature readings and work out a better solution - maybe some way of opening and closing the cooling flaps in the fan housing would be a better way to go

  • Cheap Chines Arduino Clones

    Saabman07/06/2016 at 08:40 0 comments

    I picked up a couple of these super cheap Arduino UNO clones - What a PITA.

    They use instead of an FTDI USB chip they use an infernal CHG340 chip yes there is a MAC driver for it but the bastard driver produces a name like this

    cu.wch ch341 USB=>RS232 fa210

    The Arduino IDE doesnt like spaces and trys to write to the device at cu.wch which of course doenst exist. The only way I have managed to get the the things to work under OSX 10.10.5 is to create a symbolic link to the drive name.

    sudo ln -s /dev/tty.wch\ ch341\ USB\=\>RS232\ 1450 /dev/tty.USB0

    thanks to My recomendation is dont waste your money on this rubbish - stick to the real deal FTDI chips and saveyour self a world of pain. note the windows driver does appear to work

  • Software

    Saabman07/06/2016 at 08:22 0 comments

    THe majority of this project revolves around the Dallas one wire temperature sensor the software for I borrowed heavily from

    Each project I work on I work on trying to imporve what I do with code and try and understand it better. This time I wanted to look more at using functions - I was wanting to try making use of the abiity of a function to return a value ratherthan use global variables but I didnt quiet get there - maybe next time.

    its a fairly sttaight forward code

    Upon power up read the temp sensor. If its less than 10deg turn the power to the choke off.

    then read the temp sensor every second untill the temp either rises to 20deg or 12000 milliseconds has passed (2 minutes) if either condition is true he power is aplied to the choke and it begins normal opperation.

    as the circuit only is required to opperate for a couple of minutes - rather than hold a relay high the whole time I decided to use the normal closed contacts of the relay - this way the relay is only energised for the 2 minutes of opperation - once the time has exipred the circuit is no longer required untill the car is next started.

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