Date: Thu, 4 Apr 2002 14:10:06 EST
Reply-To: FrankGRUN@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Frank Grunthaner <FrankGRUN@AOL.COM>
Subject: Re: oil and fuel level sensors
Content-Type: text/plain; charset="US-ASCII"
In a message dated 4/4/02 12:46:29 AM, cchiang1@yahoo.com writes:
<< Frank:
I'm almost afraid to ask: how did you make senders for low levels of fuel and
oil?
Cary
>>
Cary and Chris,
I'm copying the reply to the list as others have asked the same question.
Actually nothing overly challenging if you're anal compulsive (added in case
SWMBO is reading these exchanges.
1). As for the oil level sensor, this was somewhat involved. I used the oil
level switch from a Porsche 944. It is a float assembly that triggers a set
of contacts as a function of the position of the float. The contacts just
short the sense lead to ground. The real hassle was mounting the sensor. No
comment for the abused AC and WBx types as I have not studied the lubrication
situation in any detail. Ditto, for the Sub guys, but with the removable oil
pan, the situation should be straightforward. (In my turbo Audi 3A buildup, I
am also mounting oil level sensors in my auxiliary sump. Here I'm using cheap
junkyard units from the second generation RX-7. Same operating principle as
the Porsche unit, but cheap and more available. Little smaller).
Anyway, I had to move the oil filler pipe on the diesel pan to clear the
belts for my scavenger pump design. So I designed and built an interface
block of Aluminum that replaces the current Al piece on the diesel pan. I
also cut and modified the oil filler tube from a 1.9L WBx engine to interface
into the side of the adapter. The oil level sensor bolts right up and goes
into the diesel pan longitudinally. I actually extended the length of the oil
level sensor so that the float was operating in the dead center of the oil
pan (longitudinally). For the Turbo Audi 3A, I've designed a set of oil
baffles for the pan to stop front to back and back to front oil sloshing.
These baffles are integrated with the oil sensor system. The adapter bolts up
to the original oil filler system port on the diesel pan. The level sensor is
set to trigger just at the level that the oil has come down to the top of the
oil pickup tube. I'm experimenting with a dual point system that will trigger
a buzzer when the proper fill level is reached so I can do away with the
dipstick hassle altogether.
2). As for the low fuel level trick, I saw an article in Electronics Now many
years ago for a circuit using a comparator IC that would trigger around a
voltage set point. Recently there was a very good and detailed article in
Autospeed about building and using a kit supplied by Dick Smith Electronics
(around $10 US) to accomplish the same thing. Simple. PC board, IC, few
diodes, few resistors, bit of solder, bit of wire and a light trigger.
I can send pdf copies of the Autospeed article and drawings of the oil filler
adapter if anyone is interested.
In answer to Chris's question about resistors needed for the LEDs, the
typical operating voltage of the LEDs I'm using is around 1.5 volts. Don't
know the resistor value, since the LEDs I buy have the small 1/8 watt
resistor as the common lead and its covered in a tenacious shrink-wrap
tubing. DigiKey will give you all the current and operating voltage specs for
any LED you would want to choose.
Frank Grunthaner
