Date: Tue, 4 Jan 2000 11:35:17 +0200
Reply-To: Juha Koivisto <juha.koivisto@TEPCOMP.FI>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Juha Koivisto <juha.koivisto@TEPCOMP.FI>
Subject: Trailer 3=>2 converter
Content-Type: text/plain; charset="iso-8859-1"
Here is the European to US Trailer converter 3 => 2 w/o voltage drop caused
by diodes. I have designed this for my own purposes. This could be the
same schema Mike mentioned.
You need:
2 pcs change over relays (12 V automotive or general)
2 pcs 1 Amp diodes
2 pcs electrolytic capasitors
some wire, connectors etc.
And it works as follows:
If the ST wire has + 12 V then both LTS/ST and RTS/ST has + 12 V.
If LTS has + 12 V then its relay is energized and connects it to LTS/ST.
If both ST and LTS wires have + 12 V then LTS is dominating.
While LTS flashes + 12 V on/off capasitor keeps relay energized during
off -periods => same tact and flashing rate as in towing vehicle.
Selecting capasitor value (voltage rating 25 V preferred):
First measure impedance of your relay.
If you have automotive relay its impedance might be 100 to 150 ohms and
general relays could be 200 to 300 ohms.
100 ohms => 3300 mikrofarads
150 ohms => 2200 mikrofarads
300 ohms => 1000 mikrofarads
These values give about 500 ms off delay to relay.
Schema:
Diode: (anode)--D|--(cathode)
Capasitor:
__|__ + terminal
|____|
-------
| - terminal
Relay coil:
__|__
|__\__|
|
Poles of the relay
(drawn as de-energized)
n/o ---o
/o--- c
n/c ---o/
GND = GROUND
TL = TAIL LIGHTS
LTS = LEFT TURN SIGNAL
ST = STOP or BRAKE LIGHTS
RTS = RIGHT TURN SIGNAL
GND ---+--------------------(white)------------------------ GND
| TL -----------(brown)----------------------- TL
|
| LTS ---+-------------------------------o
| |
/o--- LTS/ST
| +--D|---+-------------+ o/
| __|__ __|__ |
| |____| |__\__| |
| ------- | |
| | | |
+---------------------+-------------+ |
| ST ---(red)---------------------------+
+---------------------+-------------+ |
__|__ __|__ |
-------- |__\__| |
|____| | |
| | |
+--D|---+-------------+ o\
|
\o--- RTS/ST
RTS ---+-------(green)--------------o
Hope this helps someone.
Juha Koivisto
88 Vanagon (Caravelle) 1,6TD (old school bus with 9 seats)
TURKU, FINLAND