I have ordered a new, smaller air pressure gauge to free up the large space the present one uses for a tachometer. I have a one wire alternator. That does not work with an alternator driven tach, does it? What do I have to do to get a working system?
Precision speed in Phoenix can fix you up www.precisionspeed.com
I don't know much about this but I did find out you canuse the diode taps on the back of the alt for a tac.
I only found this out trying to figure out what the 3 extra treminals on the back of my 1 wire alt was for.
I am still trying to figure that stuff out so I can wire my tach.
Check out this posting you might find the links in it usefull. I don't know how to make it a link you can search for it in the serach box on top of the page.
Re: Alternator mounting bracket « August 04, 2008, 04:05:27 PM »
Lin
If you have a 1 wire Alt - then I guess it's not a gear driven/oil coolded Detroit diesel 50DN alternator
if it was--
" Detroit Diesel Delco gear driven 50DN 270 Amp 24 volt alternators "R" Terminal hookup
The "R" terminal output is 12 volt -
Most 6V92 / 8V92-->(2.94 (53/18) gears & 6 pulses per rev=17.66 pulses/rev)
Most 24 volt - 8v71->(2.75 (55/20) gears & 6 pulses per rev=16.5 pulses/rev)
Most 12 volt - 8V71>(2.29 (55/24) gears & 6 pulses per rev=13.75 pulses/rev) "
alternators (12v or 24v) output an INVERTED sine wave - an inverted sine wave means both sine waves are a positive wave
- the normal negative wave gets flipped (inverted) to be postive - this doubles the pulse rate (the wave now has to swings between 0 and (+)
If you can determine your pully ratio - most alternators will output 6 pulses (waves) per revolution and if your tack is settable (switchable or adjustable) then it should work - If It's belt driven and the belt is tight (no slippage) then is should work
If it's 24volt output - a simple voltage divider 2 resistor circuit will bring it down to 12volts (most tacks will safely "clip" overvoltage spikes anyway)
Pete RTS/Daytona (clear as MUD - call me - ...386..672.0571...
Pete,
Yes, it is not the original alternator. I took it off last week to check to have a local shop check it out. They said it was in good condition. It is a 24 volt alternator, but it must have been built by a shop. The number on the casing is for something else and the casing opening for the voltage regulator plug is seal over with what seems to be a very tough silicone. It is only 45 amp, a far cry from the mighty 50 DN. However, since I do not run any large loads, I don't think it is a problem. I do not have any tach as of yet, so am a clean slate on what system to use. Obviously, I want to save as much cash as possible, so it an alternator driven system works, I would be happy to go with it. I think the pulleys were 7 inch on the engine and 2 or 2.5 on the alternator. Of course, I could verify this. I will call you tomorrow. Why would I want to reduce the voltage?
you only need to reduce the voltage pulse going to the Tach - although mosts tacks SHOULD have a voltage "clipper" - just to be safe ??
Instead of using the signal from a belt drive alternator that is eventually going to slip, why not use a "tach signal generator" off of the tach drive? Or, use a hall effect sensor from the crankshaft or fly wheel?
Just a thought.
Dallas,
I'm all ears. How does one find where to install these sensors? As you can see, I haven't the froggiest. No doubt I will end up learning something on this upgrade.
Lin, depending on what make and model of tachometer you have, you can use an aftermarket sensor called a Hall Effect sensor on either the crankshaft, flywheel or even one of the camshaft pulleys.
What a hall effect sensor is, basically, is a magnetic pickup that if used on the flywheel creates a small electric voltage as each flywheel tooth passes it.
You will probably have to drill a hole in the side of the bell housing, and use a bottoming tap to thread the hole for the sensor, since the flywheel teeth are really close to the edge of the bell housing, then all you need to know is the number of teeth in your particular flywheel and set your tach for that number of pulses.
If used on the crankshaft vibration damper, the idea is to glue a small, flat magnet to the damper and build a mount so the sensor can read the pulses of the magnet as it passes by. In this case the tach would be set to one pulse per revolution.
The other method I spoke of was called a "Tachometer Signal Generator." It is basically a small DC generator about the size of a D cell battery that screws on to the tachometer mechanical drive of your engine where in a truck the mechanical tach cable would go. This is usually on the back side of the engine on the end of the blower. The generator has a + and a - on it and you hook your input wires from the tach to these terminals, set the tach for the proper number of pulses per revolution and, ZIM-ZAM-Diddydiddy-Bop.... you have a tach that is very stable and very accurate.
I have a Tach signal generator on my engine that I will hook up my tach to since I don't have the 50DN alternator either, I still have the old dual field 12 generator.
My tach is from VDO and I bought it on eBay for about $20. The part number is 333 561 and reads 0-3000 rpm with an hour meter.
http://usa.vdo.com/NR/rdonlyres/8F16392C-A53E-4776-AC92-C5CC3EE9F65F/0/marine_instruments_brochure.pdf