Regulating Dashboard Voltage

[Uniflite32]

I have a 1973 65 HP Evinrude with a Stator. Voltage at the dash reads up to 17V after the engine runs for a while. This is enough voltage to fry some electronics. Is there a simple voltage regulator made that can be installed in the main power wire to the dash to limit voltage to 14V? I need to know a part number and purchase location. Thanks!

 

[Rob454]

Re: Regulating Dashboard Voltage

You can use a resistor. They do get hot. You can also use a transformer but thats usually for 120 to 12v
Rob

 

[bruceb58]

Re: Regulating Dashboard Voltage

You can not use a resistor or a transformer. Transformers only step down AC and a resistor will drop varying amounts of voltage based on the current that is being drawn.

The problem with most regulators is that you needs some "headroom" in order to regulate down to 14V. In other words 17V can easily be regulated down to 14V but 15V might be tough.

Are you measuring 17V with no load? The reason I ask is that it is possible to put a small load on the circuit to find what the loaded voltage is. It may be a lot lower than 17V and you may not have to do anything.

 

[SuzukiChopper]

Re: Regulating Dashboard Voltage

EDIT: I should mention that you should check to make sure your motor's regulator is operating properly before taking my advice. You could very well have a bad regulator and that may all you need to get a properly working system.

There really isn't too much to worry about if your voltage hits 17v at the dash. 99% of the electronics that you will have will have built in regulators because they'll run off of cmos or ttl chips. Those are only good for 3.5v +/- 1v for cmos, and 5v +/- ~3v for the ttl chips. Many of these regulators will be good from anywhere between 9v (why they still work with somewhat drained batteries) and depending on design upwards of 30+ volts. The thing that fries electronics is the amperage to the different chips, transistors, etc. Yes, increased voltage or decreased resistance causes increased amperage but most well built regulators have ways to bleed off excess voltage at the input and maintain a steady output. Best example I can give is a stun gun that can output 10k+ volts and not kill you because the amperage is low. Amperage kills you like it kills electronics.

If you are really worried, fuse each piece of electronics you have on it's own circuit, measure the amperage of that and use a 7812 (I believe) 3 pin regulator rated at the proper amps that you need (I think they go up to 10 amps or so, maybe more. digikey.com is a great source). You will need to use one for each circuit and a google search will show you schematics of out to build a proper regulator from it using prototype board. Some work, but inexpensive.

 

[bruceb58]

Re: Regulating Dashboard Voltage

Suzuki,

7812 is a bad idea...first off...max current they can put out is maybe 1A...not 10A. Second..if the input voltage is really 17V, you are dropping 5V across the reg which means the reg is dissipating 5W...that is not good and you would need a very large heat sink.

 

[bruceb58]

Re: Regulating Dashboard Voltage

Many early outboards have unregulated outputs. If this is the case with yours, you can find regulators that were put on later models.

There is a battery hooked up to this motor right?

 

[SuzukiChopper]

Re: Regulating Dashboard Voltage

Suzuki,

7812 is a bad idea...first off...max current they can put out is maybe 1A...not 10A. Second..if the input voltage is really 17V, you are dropping 5V across the reg which means the reg is dissipating 5W...that is not good and you would need a very large heat sink.

A 7812 alone won't do the trick however there are MANY circuits you could build using a 7812 to supply a regulated 12v that WILL handle 10+ amps. MOSFETs are a great choice for doing this that will allow a minimal current feed from the 7812. This is why I suggested a Google search to find the right schematic to build a proper regulator. Sorry, it's been a while since I've seen the specs on a 7812, seemed to recall that one model could handle higher amps.

Either way, most well built electronics will be internally regulated and will withstand higher input voltages within reason.

 

[bruceb58]

Re: Regulating Dashboard Voltage

Either way, most well built electronics will be internally regulated and will withstand higher input voltages within reason.

Unless you are the designer of the instrument, you can not say that. You have no idea what margins the original designer designed into the circuit. For example, voltage regulaters that were designed to dissipate a certain wattage @15V may not have heat sinks to dissipate the extra wattage @17V.

 

[SuzukiChopper]

Re: Regulating Dashboard Voltage

Unless you are the designer of the instrument, you can not say that. You have no idea what margins the original designer designed into the circuit. For example, voltage regulaters that were designed to dissipate a certain wattage @15V may not have heat sinks to dissipate the extra wattage @17V.

Actually, even if you didn't build the circuit, you can still tell what margins are built into the circuit. Data sheets for the chips used are available and the circuit they are in can be analyzed to see what the maximum values are. Not something an amateur would do but can be done.

Anyways, there is no doubt that 17v on a 12v system without proper regulation will wear it out quicker, the original poster hasn't mentioned anything blowing up yet so I'm just tossing ideas out there. Let's leave it at that. If I have to get down to the nitty gritty technical details with full blown schematics and ideas I will. I'm just dumping first hand knowledge and tips.

Here's another one, get a motorcycle regulator....... say one from a Honda CB750 or Suzuki GS1000, hook it up and there you'll have a regulated 12v to 14.5 volts.

 

[bruceb58]

Re: Regulating Dashboard Voltage

Here's another one, get a motorcycle regulator....... say one from a Honda CB750 or Suzuki GS1000, hook it up and there you'll have a regulated 12v to 14.5 volts.

That's the best thing you have said yet!

 

[SuzukiChopper]

Re: Regulating Dashboard Voltage

That's the best thing you have said yet!

Like I said, just tossing stuff out there until something sticks It's all valid advice and all of it could be made to work. Money, time and knowledge will be the determining factor in any of it. Hope you're having a good weekend and if you're a hockey fan, hope you're enjoying the game tonight

 

[bruceb58]

Re: Regulating Dashboard Voltage

Oh man...are they still playing hockey?

 

[drewpster]

Re: Regulating Dashboard Voltage

Uniflite, Check all connections from the battery to the stator especially those at the regulator. A bad connection can cause overcharging. my 2 cents.

 

[bruceb58]

Re: Regulating Dashboard Voltage

The million dollar question is if a 1973 65 HP Evinrude actually has a regulator

 

[drewpster]

Re: Regulating Dashboard Voltage

All I see listed by the suppliers is rectifiers.

 

[cjames]

Re: Regulating Dashboard Voltage

what would be wrong with an external regulator?

http://www.fisheriessupply.com/onli...ode+matchpartial+rel+Inactive/act/A01/Ntk/All

I cant believe that youre actually seeing 17 volts to any components, I would think that the batterys would buffer any charging spikes. I dont imagine the batterys like it very much. The regulator would instal between the alternator and the battery.

 

[ricksrster]

Re: Regulating Dashboard Voltage

http://www.iboats.com/CDI_Voltage_R...26209759--list_time.1179090478--view_id.47455