Joe, I need a 3 volt Dc supply!!

[laatsch55]

Joe I have to power some radios for the field. I'm starting with 12 volt DC or 120 AC. What is the fastest , cheapest way to got to a regulated + 3.0 volts DC?

 

[orange]

Find a wall wart at a thrift store, or ask one of us. How many amps are you going to draw anyway?

 

[laatsch55]

80 milliamps..

 

[orange]

Plug type, or do you just splice it like me?

 

[premiumplus]

Mouser or any supply house sells dc regulators cheap. You can hook it up to a 12 volt supply or run it off a vehicle...they're easy to implement.
An LM317 is an adjustable voltage regulator that you set up with a couple of resistors to whatever supply you need, and they're very cheap.
Another alternative is a small adjustable dc power supply.

 

[jbeckva]

Here you go. (Yeah Joe.. check my work hehe)

 

[Gepetto]

Order these from Mouser, 78M33

http://www.mouser.com/ProductDetail...=sGAEpiMZZMuLLNXTG1MZarYIFTouWOpuU1Q6hYm1KRA=

3 parts, this regulator, one 0.1uF cap on input, one 0.1uF cap on output. Short circuit and thermally protected inside the TO-220 regulator device. Simplest and cheapest solution to convert your 12V down to 3V. 3.3V is an industry standard regulated voltage Lee. This will allow some drop in your wiring and you will still be at the voltage you need to run this gear.

 

[laatsch55]

Thanks guys..All it has to do is supply a tiny transmitter to replace a lithium battery. For whatever reason the standard 3.6 volt lithium is too hot. And 3.3 is borderline. I'm reusing some fiberglass jct boxes to house then to be transmitted and received thru and they both have a regulated 12 volt dc supply already in them. The receiver/relay module requires just 12 volts and nothing more. Appreciate it fellers.

 

[Gepetto]

Thanks guys..All it has to do is supply a tiny transmitter to replace a lithium battery. For whatever reason the standard 3.6 volt lithium is too hot. And 3.3 is borderline. I'm reusing some fiberglass jct boxes to house then to be transmitted and received thru and they both have a regulated 12 volt dc supply already in them. The receiver/relay module requires just 12 volts and nothing more. Appreciate it fellers.

Then put a 1N4004 series diode on the output Lee if your application cannot tolerate that. Are you sure that is the issue? Cobalt Oxide based Lithium batteries usually charge at 4V and above which will be seen by your electronics. I assume this is a rechargeable application.

Another thought if it is just to much voltage, just put the 1N4004 in the battery output before the transmitter. That is your cheapest, easiest solution.

Clearly voltage regulation is not key to this application if it is running on a battery.

 

[laatsch55]

There is no charger in the design.its a small security system that we are using as a comm circuit. Not very robust , just something to get us by till I can get some comm cable buried. Your suggesting a 4004 to take advantage of the voltage drop to bring the 3.6 to 3.1 then..

 

[laatsch55]

Here you go. (Yeah Joe.. check my work hehe)

View attachment 15128

Thanks Jer. That would work for our flow meters..

 

[Gepetto]

There is no charger in the design.its a small security system that we are using as a comm circuit. Not very robust , just something to get us by till I can get some comm cable buried. Your suggesting a 4004 to take advantage of the voltage drop to bring the 3.6 to 3.1 then..

Yup, easy if no charger is involved Lee. That will prove if it is the 3V thing or not.

 

[laatsch55]

It really is.....It measures 3.15...but they are impossible to get in town and I have a bunch of D cell 3.6's...

 

[jbeckva]

It really is.....It measures 3.15...but they are impossible to get in town and I have a bunch of D cell 3.6's...

I .. hmmm... well...

Lee how about a couple of good ole regular D cells that put out 1.5 apiece, with a cheap ole ratshack D 2 cell battery holder? Or would they go dead too quick with 80mA?

 

[laatsch55]

The receiver/transmitter only shake hands every 3 minutes so 80ma should last a couple years...on a D cell

 

[laatsch55]

I .. hmmm... well...

Lee how about a couple of good ole regular D cells that put out 1.5 apiece, with a cheap ole ratshack D 2 cell battery holder? Or would they go dead too quick with 80mA?

Not a bad idea though...

 

[Gepetto]

It really is.....It measures 3.15...but they are impossible to get in town and I have a bunch of D cell 3.6's...

Amazon sells them Lee.

 

[laatsch55]

Thank you Joe. Guess if I put a little effort in it I could have found those, and inreality the battery shouldn't be half gone before I get some new cable buried. We have to upgrade our 2" transfer line to a 3" anyway this summer so i'll just bury some cable with the new glass line..

 

[jbeckva]

Some pretty amazing (and scary) things can be done with these things and custom linux firmware.. heheheh

 

[laatsch55]

All I need is 2500 feet line of sight with one NC contact on each end..