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General Discussion
Started by Blindstitch2002 at 01-28-2009 5:20 PM. Topic has 5 replies.
  
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 01-28-2009, 5:20 PM
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Blindstitch2002
 
Joined on 05-16-2007
Greenfield Wisconsin
Posts 5,000
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How to build a 7 volt regulator.
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Snagged from Reg in Bristols site.
Alternative 7V Voltage Regulator (AVR)
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
Heres 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.
HOW IT WORKS
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.
Thats near near enough.
A red LED will give about a 6.5V output, yellow 6.75V
so use green OK?
The heatsink is essential !
The chip has to dissipate heat and a heatsink 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.
Soldering:
Dont overheat the 7805 or LED !
this may damage/ruin them.
Tin the cable ends and legs with solder then the breifest touch with
the iron should attach them to the 7805 and LED
I use heat transfer compound when fixing the 7805 to the alloy heatsink
with a small nut and bolt or pop/blind rivet.
I also test it before potting the circuit in epoxy or hot melt glue
Heres 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 heatsink shorts to
ground, the output will drop to 5V as this will in effact 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
1978 Honda Cx500 Maggot
1979 Honda Cx500 Custom
1980 Cx500 Deluxe
Buy HTTA Items
Quick Reference Info
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01-28-2009, 5:22 PM
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Blindstitch2002
Joined on 05-16-2007
Greenfield Wisconsin
Posts 5,000
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Re: How to build a 7 volt regulator.
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01-29-2009, 4:46 PM
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marshallf3
Joined on 01-12-2009
Oklahoma City
Posts 1,526
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Re: How to build a 7 volt regulator.
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You can leave out the LED and ground the case of the regulator IC (for better heat dissipation) buy simply using a true 7V regulator IC:
755-BA17807T from http://www.mouser.com
(Where no customer or order is too small)
Look around their website you'll find all sorts of neat things to keep around like heat shrink, switches, relays, lamps etc
1979 CX500C
░░░░░░░
96 & 98 GTP, 78 Chevy G30 400V8, 78 Gremlin 304V8, 65 Barracuda 273V8
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07-26-2009, 7:13 PM
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George in Indiana
Joined on 03-03-2006
Posts 953
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Re: How to build a 7 volt regulator.
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This repair also works perfect on the CX Turbo. Just finished it earlier today and hit the road with no issues.
Some tips while this is fresh in my mind:
Failed regulator only effects the temperature and fuel gauges.
To test the regulator:
Lift the bonnet and remove the headlight assembly.
Looking down from the bonnet side you'll see the gold metal regulator right in the center.
In the headlight area you'll see the three wires that lead out from the regulator, Black/Brown, Green, Green/Black.
With ignition on, you should have 12 VDC between Black/Brown and Green (easy to check as there are bullet connectors right there). If no 12 VDC, you have problems elsewhere.
Between Green and Green/Black you should have 7 VDC. The Green/Black wire heads to the left were the gauges are and attaches to a nut behind a fairing frame tube. Put your meter probe on that being careful to short anything to ground.
No voltage or way above 7 VDC means a dead regulator.
To remove the regulator unplug to the two wires at the bullet connectors. The Green/Black wire is going to be impossible to remove from the cluster without taking apart the dash. I'm all for keeping things original but screw that, I cut the wire near the others and installed an insulated bullet connector.
The real fun is getting the regulator out. There are two phillips screws that are next to impossible to get to without removing the cluster. Luckily my Craftsman offset screwdriver was small enough to just fit inside there and get the two screws out.
Once the regulator is out you'll notice the guts are potted in and it's like concrete. I put the regulator in a vise and used my heatgun on high to heat up the metal body and potting compound while driving in a screwdriver near a side till it hit bottom (be careful not to melt the long rubber gromet that the wires go through as you'll reuse it). With a bit of prying the extremely hot compound brakes apart. Wear safety glasses while doing this! The metal shell will be nice and clean and you'll be able to save most of your wires.
Build the new regulator as above. Green wire will go to the center (LED). Black/Brown to the left leg and the Green/Black to the right leg.
The CXT regulator housing is metal and it already has a hole in it where the old components attached. Use some heatsink compound and secure the regulator to the metal housing with a small screw and nut. This is your heatsink. No need for an isolator as the regulator body attaches to the fiberglass support.
Once everything is tucked inside the housing, I tested it to make sure it works and then filled it with CLEAR hot glue.
When the regulator is reinstalled, there is an air gap on the bottom. In the future you can pop the bonnet and see the LED glowing for a quick diagnostic.
I used the parts listed above from Radio Shack and the total was $3.30. They don't carry the 2 amp regulator but I don't see a problem with the 1 amp as the housing doesn't even get warm.
Everything looks completely original and output voltage while hooked up with bike running was 6.95 volts. Can't ask for anything better than that!
CX500 TURBO
CX650 TURBO
'04 GSX1300R Hayabusa
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07-26-2009, 9:18 PM
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Dex Sinister
Joined on 11-15-2006
Durham, Cali-forn-ia
Posts 564
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Re: How to build a 7 volt regulator.
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07-26-2009, 9:24 PM
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pwtsvwt
Joined on 08-10-2008
Richfield, NC, USA
Posts 664
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Re: How to build a 7 volt regulator.
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"Okay, so where's the physical location of the regulator on a GL500I?"
Beneath / below the Tach, hanging in a rubber mount. You can't see it because of the fairing.
Bought on Craigslist - Restored from Ebay: 82 GL500I - now without the "I"
--------------------------------------------------------------
I had all my ducks in a row, but they wondered off!
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Honda CX500 & G... » CX500 GL500 Tra... » General Discuss... » Re: How to build a 7 volt regulator.
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