ZD28 Voltage Regulator Trigger Voltage

[griff04]

Still working on a charging issue with my mower.

Can someone explain the functionality of the “trigger voltage” supplied from the key switch to the voltage regulator.

Is it closing some type of internal contacts or exactly what does it do?

TIA

 

[GreensvilleJay]

I just downloaded the WSM and no mention of a 'trigger voltage' and the wiring diagram looks 'normal' to me...NO special wiring from key switch to regulator.
Happy to help if I can but need more info ,diagrams or links to what you're asking about.

 

[Soopitup]

The basic gist is,

When you pass wires through a magnetic field (or pass a magnetic field across wires) it creates electricity. The more wires and the stronger the magnetic field the more electricity you make.

Your alternator stator (think of it as a sleeve made up of a bunch of wires wound tightly together) creates the electricity when the rotor (that part that spins inside the "sleeve", rotated by the belt) spins inside of it, rotating the rotors magnetic field through the wires in the stator.

Your alternator rotor (the part that spins) is an electromagnet, not a regular magnet. It only creates an magnetic field when it has electricity flowing through it.

You can't change how many wires are in the alternator; you can change how much current (and therefor the magnetic field) goes though the rotor.
The voltage regulator "regulates" how much current goes to the rotor (this is your "trigger" current). The more current required, the more current is passed through the rotor, creating a stronger magnetic field.

 

[griff04]

I just downloaded the WSM and no mention of a 'trigger voltage' and the wiring diagram looks 'normal' to me...NO special wiring from key switch to regulator.
Happy to help if I can but need more info ,diagrams or links to what you're asking about.

Hi Jay, thanks for the reply. I’m attaching a pic out of the FSM, am I reading it wrong? It shows a circuit off the ignition running over to the regulator. Also, I thought read somewhere, hard to remember since I’ve read so much, that the regulator needed some type of trigger voltage…I may be mistaken though???

 

[Dave_eng]

Hi Jay, thanks for the reply. I’m attaching a pic out of the FSM, am I reading it wrong? It shows a circuit off the ignition running over to the regulator. Also, I thought read somewhere, hard to remember since I’ve read so much, that the regulator needed some type of trigger voltage…I may be mistaken though???

You have gone off in the wrong direction.
Your machine, like many Kubota's has a dynamo to provide the charging current. This is not an alternator!!!
A dynamo is like the light you had as a kid on the front of your bicycle rubbing on the tire sidewall.
It had some permanent magnets that rotated around a coil of wire. The magnetic field generated a voltage as it cut through the coil of wire.
The dynamo is working the same way. It has two wire coming off it, both the same color. It produces an alternating current i.e. AC voltage.
The square electronic box that the two dynamo wires connect to is doing two jobs. It is rectifying the AC output of the dynamo to DC or direct current which is needed to charge the battery. It is also limiting the max voltage going to the battery using a ZENER diode.
The dynamo's rarely fail. The regulator/rectifiers do fail.
Forum member Lugbolt has created a troubleshooting guide for dynamo charging systems which I have attached.
In the early days of Kubota's such as B6000, B7100, the regulator rectifier was very simple and had no warning circuits to tell you the battery is not being charged. Over the years additional features have been added by the dynamo has remained a simple device.
Try following Lugbolt's method. Certainly come back if there are things you do not understand.
Dave

 

[GreensvilleJay]

Ah, English is such a wonderful language......

To me ...

A mechanical to electrical changing device called an 'alternator' produces an AC voltage.

Similar device producing a DC voltage is a 'generator'

A 'spinning magnets' device on the far side of the pond is called a 'dynamo' , but here in North America it's an 'alternator', typically found in riding lawnmower engines.

I'll have to redraw the diagram, curious they have a 15A fuse that feeds the transistors that power the charge light.
One critical detail is that the case of the regulator must be cleanly grounded NOT just the 'black wire ground'. Still I don't see HOW the 'regulator' actually works,as they don't show any 'control' feature, just a full wave bridge( 4 power diodes) to convert the AC into DC going to the battery.

OK, looked at the diagram again...seems they drew the 'ic regulator' internal wiring wrong. Resitor of 2nd transistor should go to the collector of 1st transistor. Still needs case grounded for 'charge light' to function though.

 

[griff04]

First off I do appreciate all the input. I understand the theory of operation between the dynamo, the regulator, and how it recharges the battery.

Can someone explain the portion of the wiring diagram that shows the main “key switch” with the wire that runs over of it over to the regulator connector?

 

[Soopitup]

Hi Jay, thanks for the reply. I’m attaching a pic out of the FSM, am I reading it wrong? It shows a circuit off the ignition running over to the regulator. Also, I thought read somewhere, hard to remember since I’ve read so much, that the regulator needed some type of trigger voltage…I may be mistaken though???

It's not "trigger" voltage in this case, it's feedback voltage. The resistors use it to help control the voltage regulator output.
"Trigger" voltage is when you need power to create a magnet, as I explained in my previous post.
I should have read the schematic before I opened my mouth. Sorry.

If you're having trouble charging, I wouldn't think that would be the issue; only if you were over charging. But, I have no personal experience with these, so take it for what it's worth.

You have gone off in the wrong direction.
Your machine, like many Kubota's has a dynamo to provide the charging current. This is not an alternator!!!
A dynamo is like the light you had as a kid on the front of your bicycle rubbing on the tire sidewall.
It had some permanent magnets that rotated around a coil of wire. The magnetic field generated a voltage as it cut through the coil of wire.
The dynamo is working the same way. It has two wire coming off it, both the same color. It produces an alternating current i.e. AC voltage.
The square electronic box that the two dynamo wires connect to is doing two jobs. It is rectifying the AC output of the dynamo to DC or direct current which is needed to charge the battery. It is also limiting the max voltage going to the battery using a ZENER diode.
The dynamo's rarely fail. The regulator/rectifiers do fail.
Forum member Lugbolt has created a troubleshooting guide for dynamo charging systems which I have attached.
In the early days of Kubota's such as B6000, B7100, the regulator rectifier was very simple and had no warning circuits to tell you the battery is not being charged. Over the years additional features have been added by the dynamo has remained a simple device.
Try following Lugbolt's method. Certainly come back if there are things you do not understand.
Dave

Jesus, are we using points ignition too?!

My understanding is that a dynamo uses a commutator instead of a voltage regulator?
I see in the diagram Kubota calls it a dynamo, and yet it has a voltage regulator. Dunno.
I have no experience with dynamos, only what I've read.
Looks like a brushless alternator to me? Lots of ways to skin a cat I guess.....

It is also limiting the max voltage going to the battery using a ZENER diode.

According to the diagram it's actually using resistors, not a zener diode.
Zener diodes have a different symbol than regular diodes.

Still I don't see HOW the 'regulator' actually works,as they don't show any 'control' feature, just a full wave bridge( 4 power diodes) to convert the AC into DC going to the battery.

The resistors are used to control the voltage, with the feedback voltage from the key on wire (yellow?).

 

[Soopitup]

First off I do appreciate all the input. I understand the theory of operation between the dynamo, the regulator, and how it recharges the battery.

Can someone explain the portion of the wiring diagram that shows the main “key switch” with the wire that runs over of it over to the regulator connector?

That is providing a reference voltage to the resistors that are controlling the voltage.

 

[GreensvilleJay]

If the diagram in post #7 is true...
there is no feedback and no control over the charging
The 2 small diodes, 2 transistors and 2 resistors are ONLY used to turn the 'charge light' off.
The wire from the ign switch provides the +12 to power this 'indicator circuit'.
Actual charging 'control' is based on battery condition. Dynamo produces AC volts, 4 power diodes convert to full wave DC, goes to battery..ZERO 'active' control..NO 'electronics' is involved.

 

[Dave_eng]

First off I do appreciate all the input. I understand the theory of operation between the dynamo, the regulator, and how it recharges the battery.

Can someone explain the portion of the wiring diagram that shows the main “key switch” with the wire that runs over of it over to the regulator connector?

 

[GreensvilleJay]

re: Can someone explain the portion of the wiring diagram that shows the main “key switch” with the wire that runs over of it over to the regulator connector?

easy.
turn key on, +12 is supplied through the 15a fuse to the emitters of the 2 transistors in the 'regulator'.
When the engine is not running, the 2nd transistor is on and the 'battery charge lamp' is on.
When the engine runs those transistors get 'pulses' from 2 signal diodes and the 'battery charge lamp' turns off.
Simply put, 'they' needed a source of switched power, otherwise the 'battery charge lamp' would be on 'forever' or until the engine was started or the battery drained down....

I have no idea why the 15 amp fuse.....5 would have been fine...

 

[lugbolt]

the "trigger" wire tells the regulator to turn on. Additionally it is also a sensing wire, so if the reg/rec sees the trigger wire voltage below the, let's say 13.5v maximum allowed, the regulator will increase the voltage until it sees that maximum. It will usually climb over that a little, before it's "told" to slow down, and the voltage output will vary a little. Most DVOM's won't see that variance very well if at all but a scope will. Sometimes an analog voltmeter.

2 wires at the reg come from the dynamo (AC output from dynamo). One wire is ground. One goes to the battery--that one charges the battery. One wire from ignition switch ("trigger" and "sensing" wire-all in one). So with that you can test each wire and see what you do or don't have.

 

[griff04]

the "trigger" wire tells the regulator to turn on. Additionally it is also a sensing wire, so if the reg/rec sees the trigger wire voltage below the, let's say 13.5v maximum allowed, the regulator will increase the voltage until it sees that maximum. It will usually climb over that a little, before it's "told" to slow down, and the voltage output will vary a little. Most DVOM's won't see that variance very well if at all but a scope will. Sometimes an analog voltmeter.

2 wires at the reg come from the dynamo (AC output from dynamo). One wire is ground. One goes to the battery--that one charges the battery. One wire from ignition switch ("trigger" and "sensing" wire-all in one). So with that you can test each wire and see what you do or don't have.

First off great write-up on checking the charging system.

I had a chance to get back on it yesterday. Everything checks out other than the charging wire off the regulator back around to the battery where I had no voltage. When checking at the connector at the regulator I have 19v that should be getting back around to the battery. With the PO “hacking” up all the wiring pertaining to the safety switches I suspect this may have something to do with it…I believe there may be a break from the charging wiring off the regulator back around to the battery.

I really hate tearing into the wiring harness that may cause other issues….do you think that it would be safe to just run a wire off the regulator back over to the battery??? Not sure if this is a good idea or not from a safety perspective!!’

Also I have a question about the wiring diagram. Why is the charging wire highlighted in green got to both the battery and key switch? Really don’t understand the concept around this.

TIA

 

[DustyRusty]

That is the main feed for the machine's electrical power system. i.e. starting motor, headlamps (if installed), etc.

 

[lugbolt]

One critical detail is that the case of the regulator must be cleanly grounded NOT just the 'black wire ground'.

not always. Depends on the design of the regulator and most Kubota's that use external regulators, do not require a case ground. Every single one of them I've dealt with will function (charge) the same whether it's bolted down or just laying there. Similarly Yamaha, Kawasaki, and a bunch of other brands of lawn mowers that use the same style regulator. While wise to bolt it directly to a metal ground, it doesn't really affect how it operates. But it does help to pull heat away from it.

For those that don't understand how they work, in laymans terms, the ac voltage from the "alternator" (dynamo) is AC voltage (alternating current). The regulator is also a rectifier. So when testing alternator output, remember that the regulator cuts the AC voltage output from a minimum of 1/2. So you want to see a minimum of 24v AD output from the alternator, if less, the alternator may be bad or wiring bad. As said, you want to use a little caution in testing the alternator output because it is AC voltage and some of them can run upwards of 60v or so at full speed, which can "bite" you. Those of us who have heart issues and/or pacemakers can have a rough time with this so be careful.

 

[GeoHorn]

Ah, English is such a wonderful language......

To me ...

A mechanical to electrical changing device called an 'alternator' produces an AC voltage.

Similar device producing a DC voltage is a 'generator'

A 'spinning magnets' device on the far side of the pond is called a 'dynamo' , but here in North America it's an 'alternator', typically found in riding lawnmower engines.

I'll have to redraw the diagram, curious they have a 15A fuse that feeds the transistors that power the charge light.
One critical detail is that the case of the regulator must be cleanly grounded NOT just the 'black wire ground'. Still I don't see HOW the 'regulator' actually works,as they don't show any 'control' feature, just a full wave bridge( 4 power diodes) to convert the AC into DC going to the battery.

OK, looked at the diagram again...seems they drew the 'ic regulator' internal wiring wrong. Resitor of 2nd transistor should go to the collector of 1st transistor. Still needs case grounded for 'charge light' to function though.

I”ve seen many references also to an “AC-Generator” , … or described as an “alternating current electrical generator”.… either of which seems more accurate as descriptions, but English being a ”living language”… contractions and psuedonyms being common.

 

[griff04]

First off great write-up on checking the charging system.

I had a chance to get back on it yesterday. Everything checks out other than the charging wire off the regulator back around to the battery where I had no voltage. When checking at the connector at the regulator I have 19v that should be getting back around to the battery. With the PO “hacking” up all the wiring pertaining to the safety switches I suspect this may have something to do with it…I believe there may be a break from the charging wiring off the regulator back around to the battery.

I really hate tearing into the wiring harness that may cause other issues….do you think that it would be safe to just run a wire off the regulator back over to the battery??? Not sure if this is a good idea or not from a safety perspective!!’

Also I have a question about the wiring diagram. Why is the charging wire highlighted in green got to both the battery and key switch? Really don’t understand the concept around this.

TIA

As not to butcher-up anymore of the wiring or the harness as the PO done I elected to just run the charging voltage wire directly off the the regulator back over to the slow-blow 40 amp fuse that supplies the battery for recharging. I’ll just have to keep a close eye on it the next time I run, hopefully I won’t burn it up.

As of now:
35VAC volts @ WOT from the dynamo to the regulator with 14.3VDC leaving the regulator back to the battery.

For now I’m going to call this a “done deal”. I may try doing something with the wiring in the off season.

Thanks for all the info and recommendations.

 

[GreensvilleJay]

I was using the schematic of the OPs machine, when I said it needed a ground, to function properly for the 'charge light' system. Even though the drawing is wrong, that 'regulator' does require ground to function for the 'charge light'.
All B&S regulators based on their 1972 patent as well as Kohler '3 terminal' regulators. These ARE combination rectifier-regulators, they actively regulate the power to the battery.
As for other mfrs/ makes, I need to see 'what's inside' to determine how they work but in this case ground is required.
According to the diagram , there is no 'electronics' to regulate the charging of the battery. AC from the dynamo feeds a full wave bridge that's connected to the battery. If the dynamo puts out 30 VAC, the FWB will convert it into about 42 VDC with the battery becoming the 'regulator'. Easy to see this when the battery is replaced with a small 'burden' resistor.