Category: Alternator w terminal tachometer

Alternator w terminal tachometer

On alternators there is a "phase tap" sometimes called a "W Terminal". What type of waveform does this give out? Is it a sine wave AC?

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Znago; some gen set manufacturers use that tap for high frequency ac for a reference to control the RPM. Just looking to understand what type of signal it is so that I can then design a conditioning circuit to give me a square wave as input to the microcontroller. Ah, you're likely to get a whole variety of answers from people here about what they think you have in your hands. I recommend you get an oscilloscope and measure what this terminal will do across a variety of different alternator speeds and loads.

I would expect that you would get a sine wave AC signal with no DC offset.

alternator w terminal tachometer

The amplitude will not be precisely constant but not varying too much over time. But I would not be surprised to find a rectified sine wave signal or even a sine wave with a DC offset so that the negative peak of the sine wave is at 0 volts. Without knowing how many poles your alternator has, you'll have to guess at the integer multiple the frequency of this W terminal produces in comparison to the alternator's rotational frequency.

Just that it is not very easy for me to get ahold of one I know it sounds strange but true So I am looking for info to get an understanding and a head start. I would not be too much concerned with amplitude I think since anyway the output should be clamped to 5v probably by a zener or something to go in to the micro.

If it is a true sine wave AC signal, is the circuit just a comperator that would give out say 5v when sine wave is positive and zero when sine wave is negative? Yes, a comparator circuit will be your ideal interface for all three of the signal scenarios I proposed. A comparator circuit will permit you to easily control input impedance so that you do not load the W signal and effect any other circuitry.

You can select a hysteresis range to reduce noise pick up.

Alternator Terminal Identification Chart

Naturally the actual resistor selection and topology will depend on what you find with the oscilloscope. If the signal is one of the three signals I proposed, then an AC coupled inverting comparator circuit will do your job. Don't forget to clamp the inverting input to return with a diode to protect the negative voltages this will produce.

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In this case it will be useless for an alternator tachometer. Long time from your post. I find it very enlighting and maybe you can answer my question.

Adding a W terminal to alternator

I read that getting signal from the alternator for RPM measure has the drawback that the signal can be lost under full battery conditions. Naturally many things can attenuate a signal to the point of making it unreadable. So as long as the alternator signal remains above or just near the noise floor, a simple comparator circuit should be able to discern it from the noise.

To extract a smaller signal from the noise will require a more refined analysis of signal and noise but you would be amazed what can be done.

Will have to test the engines under full battery conditions and see what happens then. Good to know I have to keep an eye on that.

So being that true, those Diesel RPM measure devices that connect directly to the battery should suffer a simmilar effect, or am I wrong?

Would you reccomend one of those? I need to know much more information to render any opinion on a specific model instrument, let alone such a loosely defined group as "those Diesel RPM measure devices".Latest Projects Education. JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. Get RPM form alternator. Thread starter szotyi Start date Feb 15, Search Forums New Posts. Thread Starter szotyi Joined Jan 14, I have a Denso alternator.

I would like to get the RPM from it. So far I have got: There is a connector:one pin is the P terminal, according to some datasheet this is the stator. I have connected this terminal to the base of a bc transistor through a 10 kohm resistor. And counting the falling edge with Arduino. It works okay, but my problem is that I have counting around pulses per sec rpm with no gas, with full gas around pulses per sec rpm.

If I divide those numbers with 12, then I would get rpm to rpm, which sounds ok. But how do I get the 12? Or is it correct? Thanks, Szotyi. Scroll to continue with content. If you just want alternator rpm Dodgydave said:.

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To divide by 12, rotate right the counting file 6 times, each rotate right divides by 2. MaxHeadRoom Joined Jul 18, 21, If the terminal is the DC output, this will have 6 ripple pulses per Electrical revolution, for 4 pole two electrical revolutions this would be Not sure if this is what is referred to?

Oh yes, you must be right. I will measure the pulley sizes, and calculate the ratio.By jrjacksoNovember 15, in Defender Forum - Looking to add a rev counter to my 2. The Vdo tachometers have multiple operation settings, they will work off the W terminal on the back of the alternator and have a potentiometer for calibration to read the correct R.

Also you could fit a diesel tiny tach, which uses a clamp around an injector line and measures the pulses to give you a very accurate reading off an LCD screen. I haven't dug around on the back of the alternator yet, but wanted to confirm that indeed the Lucas A has a W terminal, to make sure that would be an option. This is my Lucas A alternator with the rear cover removed. I assume attaching to any one of the three bolts I have indicated with the white arrows in this photo will work.

Those bolts seem to hold three diode packs in place, they probably screw into the case frame, chassischeck with a multimeter. The bolts are probably insulated from the diode pack.

Try to locate the thick wires coming from each stator field winding. You may only be able to see one wire from each, but that's fine. Those wires will be heading towards those diode packs. They 'may' even be electrically connected to those bolts making my 'No' wrongbut I very much doubt it. It is one of those wires you need to connect to, perhaps you will have better access from the side, rather than the end, shown in your view.

The attached diagram MAY help, but you probably need additional information, as it doesn't show the connection of the stator wires to the 'diode plate'. Can't see it really in this photo, but there is indeed a wire 3 coming out and soldered to each of the plates under those 3 bolts.

Oh, I did test continuity between the plates diode pack and the bolt and they are isolated from one another. OK, I did the written answer, and then went looking for more information, so it was some time later I found the exploded diagram. When I saw there was a 'diode plate' I did think my surmise of those screws going into the frame might be wrong. Two alternatives come to mind, one is dependant on the access available while the alternator is mounted.

On the bench, see if you can get one meter lead on the point the wire terminates, and check for continuity to the bolt head.

alternator w terminal tachometer

You might have to determine which screws hold the diode plate in place, and remove them so you can lift the diode plate away to give access.Any content, information, or advice found on social media platforms and the wider Internet, including forums such as YBW, should NOT be acted upon unless checked against a reliable, authoritative source, and re-checked, particularly where personal health and liberty is at stake. It is your responsibility to provide references to bona fide sources.

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What's new New posts Latest activity. Log in Register. Search titles only. Search Advanced search…. New posts. Search forums. Log in. JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. Adding a W terminal to alternator. Thread starter martinriches Start date 24 Nov Joined 8 Jun Messages Location London.

I need to open up my tachometer to add a W terminal which will be a sensor for a Faria tachometer. It is a a Hitachi 35a from a Yanmar 2GM I have found some information on how to do it which seems fairly simple. It wasn't however on this particular alternator. Has anybody made the connection on the Hitachi? VicS Well-known member.

Boat: Chichester. Hitachi alternator: P is the "W" connection. Thanks Vic. There are two other unnamed terminals but they have no effect on the tacho.QRZ Forums.

Hello all, This is not ham radio related, but since there are so many very knowledgabe folks here, maybe I can get some ideas. I have an older sailboat boat with a diesel engine. The alternator is a 45 amp 65 amp? Been using that type of setup for most of the 29 yrs I've had this old boat. The tach is driven from the Stator post on the alternator. As you know, the tach "reads" the freq of the AC voltage from the alternator that varies with the alternator speed.

The amp meter had broken a yr or so back - since I didn't use the boat a lot it didn't matter since I knew the alternator was charging because the voltmeter was showing high voltage.

The tach was indicating high. This morning I purchased a new voltage regulator and installed - then the tach started to read low after a few minutes. My problem is the tach now seems to indicate based on the alternator output.

The tach signal sensor is connected to the STA terminal on the alternator. When the alternator is putting out max output 50 amps or so, the tach reads fast Just a approximation there. As the alternator drops back to normal charge, the tach slowly drops to read low when the alternator is barely charging - perhaps rpm where it should be rpm? The voltage then goes thru the diode bank where it is converted to DC voltage to charge the battery.

The Stator terminal is where you connect the tach sensor so it can read the freq. What we're looking for here is under what conditions can the stator change freq based on charge rate?

There should be no condition that could happen, but that's what seems to be happening. I do not understand it myself.

I had a hard time writing it up so it made sense - I hope this helps understand the problem? Has anyone ever seen anything like this happen? Any ideas what can cause this to happen? Thanks to all for any and all suggestions. Last edited: Jul 16, K9FVJul 16, I put a similar tach on a Chev Diesel pickup.

Never had the problem you describe. Sounds like time to replace. They are not very expensive, as I recall.

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KD7HBJul 16, Since the alternator is charging nicely, and the tach is actually only reading the freq of the AC voltage before the diodes - what do you think could be bad in the alternator? It's only a yr or so old Any chance the fan belt is slipping? It would slip worse when the altertnator is supplying more current; then it would slip less as the load tapered off.Any content, information, or advice found on social media platforms and the wider Internet, including forums such as YBW, should NOT be acted upon unless checked against a reliable, authoritative source, and re-checked, particularly where personal health and liberty is at stake.

It is your responsibility to provide references to bona fide sources. Forums New posts Search forums. What's new New posts Latest activity. Log in Register. Search titles only. Search Advanced search….

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New posts. Search forums. Log in. JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. Alternator connection for tach. Thread starter dgadee Start date 5 Apr Joined 13 Oct Messages 1, My engine has had a replacement alternator installed by the previous owner and the tachometer doesn't work at present.

My understanding is that to connect up the tachometer from the switch panel it needs a fourth connection usually w and this is shown in the engine wiring diagram below. Is this true? Or do I just use one connection - R? Your link doesn't appear to work. I would think that the "R" terminal is connected to the internal regulator, and extenally to the "ignition switch.

It is for Hitachi alternators anyway. The other terminals connect to the battery one way or another and will not give the frequency signal.

Should have said that. VicS Well-known member.

alternator w terminal tachometer

Boat: Chichester.Pages: [1]. This is my first post so please bear with me. I'm trying to drive a tachometer three prong, three phase from an old airplane from the engine's alternator. It being a mechanical diesel I have to run it off of the alternator's W terminal, which is one of the three phases.

I'm trying to figure out a feasible way to get this as a stable input to the Arduino, in this case an Attiny13a, to basically calculate the proper PWM signal to drive the electronic speed controller to drive the tachometer. Edit: Found a solution using a 5v zener, resistor, and capacitor shown below. A tachometer converts mechanical power into a small electrical signal for measuring rotation speed - yet you talk of "driving the tachometer" from an alternators W terminal?

Do you mean you are trying to drive a tachometer's meter unit? IE replace the tachometer with a different signal source? Quote from: raschemmel on Jul 16,am. Quote from: PerryBebbington on Jul 16,pm. Quote from: MarkT on Jul 16,pm. After some more research I've decided to go a different route, ditching the opto-coupler. I had to pull apart my alternator and solder in a output for the W terminal as there was no terminal there, but there was a cutout for a terminal and a casted W right where it should be.

Few long screws and some solder later and it was done. I used a 5v zener, 4. Uploaded the attached code and it works! Now all that's left is to get a laser rpm meter and make sure it's reading correctly, and then figure out a driver for the gauge as the ESC doesn't want to power it.

Quote from: raschemmel on Jul 25,am. Where did you get that diagram from. It won't work. Impossible to drive mosfets with that. Are you trying to do something like this? Quote from: Wawa on Jul 25,am. Right, there must be a three-phase motor inside that instrument that needs to be powered with some sort of VFD variable frequency drive.

Should be able to do that with H-bridge chips, as in the link I gave you.

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