Home made 7v Regulator(Courtesy of Reg )+ Test

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Home made 7v Regulator(Courtesy of Reg )+ Test

Postby Gman » Tue May 05, 2009 3:27 pm

Note:If the bracket on top of the thermostat that screws into the engine(not the two bolts that hold the thermostat top) is loose or not grounding correctly you will get a,"High" reading on the Temp gauge.

Quick test

1:Set Multimeter to 20v DC range.

2:Open the green/blue leads connector to the rear of the thermostat under the tank and
measure the voltage form the gauge when the ignition is on to the frame/ground.

It should be around 6.75v to 7v DC

If this is ok suspect the sender unit itself which is housed in the the thermostat housing.

Alternative 7V Voltage Regulator

Warning!!!.Only use 5mm Green LEDs.Not any other size.

The 7v regulator is used to give a steady power supply to the
Temp and Fuel gauges.
They can often give a high output when failing and overdrive the gauges
This can get you pulling the cooling system apart before you realise
you have a fault in the Regulator
I find the easiest way to check the output is to take a reading on
the bullet connector to the rear of the thermostat with the ignition on.
It can be done with the tank on but its no big deal to remove the tank
on a ZAB type CX.
In the pic below is a failed regulator.
The red arrow points to a split in the casing due to overheating.
The other one has my DIY version fitted into an original case.
I usually try and use the original leads too.
but in this case they had been chopped off.


I have had a couple of these on extended test for quite a while now
with no problems reported.

Component cost is about £1
Here's the circuit

Crude maybe,but effective and pretty damn reliable too
the fuse is optional and so is the 0.1uf cap on the output.


The chip controls the output voltage with reference to ground.
So, what we do is bump up the ground by putting a green led between
the 0V pin and ground. This usually gives around 6.95V.
That's near near enough.
A red LED will give about a 6.5V output, yellow 6.75V
so use green OK?
The heat sink is essential !
The chip has to dissipate heat and a heat sink will allow it to
do that without damage
The output cap is non essential, its a crude circuit and
minor fluctuations will go unnoticed.
I've never bothered to fit them.
The 7805 IC is common as muck and cheap too.
It is rated at 1 amp and the 78S05 2 amps.
If I wanted to drive two gauges I'd use the 78S05.

Assembly tips:
The 7805:
When laid on its back the pins are from left to right
Input (red)- Ground (green) - Output (yellow) The input connects to ignition live which on the CX is a black cable
The Ground has the green led between itself and ground
Output goes to the temp gauge
____________________________________________ The green LED
The longer leg is the anode or positive leg (red arrow).
this is the leg that must attach to the centre pin of the 7805.
the shorter leg is the cathode (green arrow).
this is usually denoted by a flat on the clear body as well.
this leg connects to ground.

Don't overheat the 7805 or LED !
this may damage/ruin them.
Tin the cable ends and legs with solder then the briefest touch with
the iron should attach them to the 7805 and LED

I use heat transfer compound when fixing the 7805 to the alloy heat sink
with a small nut and bolt or pop/blind rivet.
I also test it before potting the circuit in epoxy or hot melt glue

Here's a pic of one on my bench
I try to keep them as compact as possible so I can fit them
into the original cases and have as large a heat sink as possible


If you use a different method, be warned that if the heat sink shorts to
ground, the output will drop to 5V as this will in effect bypass the LED and it will behave like a normal 7805.

Insulator kits are available for this type of IC and cheap too should you want to use them
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Re: Home made 7v Regulator(Courtesy of Reg )

Postby torgo » Mon Apr 19, 2010 7:08 am

If you don't want to build one Digi-Key has a 7V reg.

IC REGULATOR 7V 1A TO252-3 TR - BA07FP-E2 - Integrated Circuits (ICs)


7V at 1Amp.
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Re: Home made 7v Regulator(Courtesy of Reg )

Postby Gman » Mon Apr 19, 2010 1:39 pm

Cool.Thanks for finding that :)
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Re: Home made 7v Regulator(Courtesy of Reg )+ Test

Postby bri-guy-ga » Sat Jul 03, 2010 2:16 pm

What do you use for a heat sink? I read in the goldwing forums that you can use a 7807 voltage regulator and not need the led or other parts. How do you get the old regulator apart?
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Re: Home made 7v Regulator(Courtesy of Reg )+ Test

Postby Gman » Sat Jul 03, 2010 3:03 pm

I didn't.I left the old one in and just bypassed it and stuck my home made on into the headlight.The heat-sink was from the same electronics supplier,dead cheap a bit like this,


Most of them will do at this size.Don't try and out-think reg on this.It works with the green 5mm Led.However as you can get the 7v regulator chips over there you can use one of them but still use a small heat-sink.

http://parts.digikey.com/1/parts/612669 ... 7807t.html

Cut yellow wire a couple of inches from regulator.Use this to the correct pin on the IC.Pull apart Green ground wire.Make small wire with bullet or spade connector as applicable to push into harness ground wire and other end soldered to Negative of the Green 5mm LED.Long leg of Green LED(Anode) to Correct IC pin(See Reg's post for correct wiring)

Pull apart Black 12v + feed from harness and same as above but to the correct pin on the IC.

I used heat shrink around legs of the IC and joints so no shorting can occur,

http://cgi.ebay.com/Pro-Assortment-Heat ... 2a083d742f

Then stuck it to my headlight with some Mastic(Blue Tac).As mine are UK CXs the Regulator is behind the clocks and an absolute Beeatch to get out so I left it in.

I also had to make a new ground wire point inside the headlight.I took the wire to a bolt/nut near the fork tops I recall.
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