SteveA
Well-Known Member
I intend fitting a monitor/alarm to the wet exhaust of my VP MD2020 engine and would like it to only be powered when the engine is running - has anyone any idea how I can do this?
Exhaust Temperature Monitor
- Thread starter SteveA
- Start date
Bav32
Well-Known Member
Pick up the 12 volt supply from the light on your fuel guage on the instument panel,
Always "live" when engine is running i.e. power on at instrument panel.
Always "live" when engine is running i.e. power on at instrument panel.
BabaYaga
Well-Known Member
If you will settle with an alarm only, one very simple way is fixing a bimetal switch with suitable rating at the exhaust bend and then connecting this in parallel with the normal engine over heat alarm. This way the buzzer will sound (and warning light come on) regardless of which of the two sensors that is activated.
SteveA
Well-Known Member
Thanks but my fuel gauge isn't powered from the engine instrument panel. The md2020 engine has quite a simple panel that doesn't seem to have any constant 12v when switched on - that's my problem.
BabaYaga
Well-Known Member
Seems quite odd to me. Surely there must be power at the ignition switch (terminal 30) or on one side of the start button?
VicS
Well-Known Member
You dont say if you have the panel with a key switch or the "standard" one one with a push on/off power switch. Presumably the latter but in either case you can pick up a switched 12 volt power supply from the red/blue wire in the panel. At the on/offswitch ( or the key switch if applicable) would be the most appropriate place to connect.
Look at the wiring diagram in your owners manual for guidance.
It would be appropriate to fit a fuse, suitably rated for your monitor and the wiring to it, in the connection especially if your exhaust monitor is any distance from the engine control panel although as you will see from your manual the supply to the engine control panel is itself fused.
You do not say what monitor you are fitting but I note that a 1 amp fuse is recommended in the supply to the Nasa EX-1
Note the red wire on the on/off switch, or on terminal 30 of the key switch if you have one, is the power to the panel and is therefore not switched.
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Refueler
Well-Known Member
Relay.
I know its a different item - but principle is the same.
My Cool box drains my batterys quickly as its the useless cheap style that really is only good for picnics. But it does for less sensitive stuff.
I used a common car relay that once engine starts and alternator kicks in - the relay closes and cool box gets power. Engine stops - relay drops out and power is cut from the box.
I would upload the simple circuit diagram to wire in - but Photobucket is down and I cannot link to the archive of my stuff. It really is simple to do ...
I have a raw wet exhaust on my Perkins .... I used to have a simple dual sensor temp display that are really designed for inside / outside display. The outside sensor being a thin wire job. I taped that to the exhaust far enough away from engine that it would not exceed max .... but close enough that it would show abnormal rise. It had an alarm .... ran of AAA battery ..... it now sits monitoring my Laser Cutter water bath !!
I know its a different item - but principle is the same.
My Cool box drains my batterys quickly as its the useless cheap style that really is only good for picnics. But it does for less sensitive stuff.
I used a common car relay that once engine starts and alternator kicks in - the relay closes and cool box gets power. Engine stops - relay drops out and power is cut from the box.
I would upload the simple circuit diagram to wire in - but Photobucket is down and I cannot link to the archive of my stuff. It really is simple to do ...
I have a raw wet exhaust on my Perkins .... I used to have a simple dual sensor temp display that are really designed for inside / outside display. The outside sensor being a thin wire job. I taped that to the exhaust far enough away from engine that it would not exceed max .... but close enough that it would show abnormal rise. It had an alarm .... ran of AAA battery ..... it now sits monitoring my Laser Cutter water bath !!
SteveA
Well-Known Member
zoidberg
Well-Known Member
I understand that very proper British firm NASA do - or did - an engine exhaust over-temperature alarm for simple DIY fitting. It may be worth exploring that offering.
Hostage
Active Member
About 2 years ago david Berry wrote an article in PBO showing how to make a wet exhaust alarm from a kit which came complete with PCB board and all the components for about £20. I made one and am well pleased.
VicS
Well-Known Member
Sorry not replied sooner ... been away for new year.
You may be able to find a connection in the engine wiring if your engine is a C or D series.
There is a switched supply to an excitation resistor on later engines ( and then on to the alternator) which is also colour coded red /blue. If you can locate this you may be able to connect to it on the supply side of the resistor, not the alternator side. ( I guess this will apply to engines with LED indicator/alarm lights in the control panel but not to those with filament bulbs)
Cannot help with the location of the resistor as I am only going by the wiring diagrams,
Molteni
Well-Known Member
I took the feed from the engine hours gauge
