Q: How to power a 5V meteorological station from my 12V launch controller

[Brainlord Mesomorph]

TL/DR: Its an electrical question; I have 12V,14A system and I want to power a 5V, 600mA accessory from it. I have found a 12V/5V DC-DC downstep, but it outputs 3 amps.
Can I use that if I add an appropriate resistor? Or what should I do?

Now, how does that have anything to do with rockets:

A couple of years ago I built this TOTALLY AWESOME launch controller (with a lot of help from this TRF thread: https://www.rocketryforum.com/threads/questions-about-my-diy-launch-controller.145459 Special Thanks to Voyager1 and OverTheTop)

It has 14AH of batteries, and a peak amperage that I have never been able to measure because it pops the 10 amp fuse. Now I gave it all that juice because I planned on powering other things from it. I’m building in an EggFinder LCD receiver (that will go in that blank space) and I’ll be adding USB DC Out for charging devices, etc.


Now I have bought this meteorological station:

The display should fit neatly in to lid of the launch controller

So, it comes with a 120VAC to 5VDC 600mA transformer.
I want to replace that with an aux power out from the launch controller. As I said above I have found this downstep at ebay
but its 3 amps and I need 600mA. So do I just add a resistor the to the output? And what resistor would that be?

 

[UhClem]

3A is a maximum limit. You do nothing.

 

[Brainlord Mesomorph]

3A is a maximum limit. You do nothing.

Sorry if I'm being thick, "I do nothing?" meaning "I can just use it as is"? or "I shouldn't do this at all?"

The 3 Amps isn't going to fry a 600mA device?

I'm still very vague on the concept of components "pulling" the power they consume from a circuit vs. batteries "pushing" power out and frying things, or whatever really happens.

 

[dhbarr]

Sorry if I'm being thick, "I do nothing?" meaning "I can just use it as is"? or "I shouldn't do this at all?"

The 3 Amps isn't going to fry a 600mA device?

I'm still very vague on the concept of components "pulling" the power they consume from a circuit vs. batteries "pushing" power out and frying things, or whatever really happens.

The device will pull 600mA and be happy. We plug low-wattage devices into 15A wall sockets all the time.

 

[neil_w]

3 Amps is the maximum power that the supply will provide. Your weather station won't draw nearly that much.

Analogy: imagine how much water your house water service could supply if you just cut the pipe open. That is the maximum. Now imagine how much flows if you only turn on a faucet. That's how much it "draws".

 

[cerving]

You could tap the 5V regulator output on the Eggfinder LCD, it's good for 1A and the display only uses about 1 mA. That's a pretty cool launch controller... I never thought of putting the LCD in one before.

 

[Brainlord Mesomorph]

The device will pull 600mA and be happy. We plug low-wattage devices into 15A wall sockets all the time.

Thanks

3 Amps is the maximum power that the supply will provide. Your weather station won't draw nearly that much.
Analogy: imagine how much water your house water service could supply if you just cut the pipe open. That is the maximum. Now imagine how much flows if you only turn on a faucet. That's how much it "draws".

I've seen the plumbing analogy many times. Voltage is the diameter of the pipe?, amperage is the speed of the water in the pipe?, and watts is amount of water moving in the pipe. I even know W*V=A.

What I don't get is why in some situations electricity will fry a component and in others it will wait calmly in a battery.

You could tap the 5V regulator output on the Eggfinder LCD, it's good for 1A and the display only uses about 1 mA. That's a pretty cool launch controller... I never thought of putting the LCD in one before.

(gasp) I never thought of that! I should build the Egg finder first, and just use it!
THANKS

 

[UhClem]

The power supply provides 5V at anywhere from 0 to 3A. (There is usually a lower limit below which they do not regulate the output voltage well but 600mA should be above that.)

A voltage regulator has a very low output impedance which means, for the non-EE types, that the voltage varies very little with load.

 

[neil_w]

I've seen the plumbing analogy many times. Voltage is the diameter of the pipe?, amperage is the speed of the water in the pipe?, and watts is amount of water moving in the pipe. I even know W*V=A.

Voltage is the water pressure. Current is the rate of flow (e.g. gallons per minute).

What I don't get is why in some situations electricity will fry a component and in others it will wait calmly in a battery.

Ohm's law: V = IR, or I = V/R. Therefore, for a given voltage, higher resistance -> less current, and vice versa.

Given a 12V supply (for example), I = 12/R. If you have a 1 ohm igniter, then you'll draw 12 amps (actually it'll be less than that, because the power supply has its own internal resistance that adds to the 1 ohm igniter, but let's ignore that for now).

To go back to the water analogy: if you connect a drinking straw to your water supply, you're simply not going to get that much water through it because that straw has the equivalent of a high resistance. Whereas if you connect a 4" pipe to it, which has comparatively low resistance, you're going to get a lot of water.

Note that complex electronic devices (e.g. your cellphone) don't have a simple value for R that you can plug into the equation. In those cases, the power supply input is usually rated for a maximum input voltage it can tolerate without blowing. That is why you should never plug a 110 V device into a 220 V outlet, unless the supply is specified to work with 220 V.

 

[Brainlord Mesomorph]

Voltage is the water pressure. Current is the rate of flow (e.g. gallons per minute).
Ohm's law: V = IR, or I = V/R. Therefore, for a given voltage, higher resistance -> less current, and vice versa.

Thank you for trying.

"Current" where is 'current' relative to watts and amps?

I do understand most of "How electricity works" What I don't get when things go wrong and how to avoid it. If I stick my drinking straw into a city water main, the pressure would blow the back of my head off. When does that happen electrically?

Specifically. this Weather Station will operate at 5V 600mA. (I'm sure a little more or less would still work.) I am being told here that providing it with a "potential" (am I using that word right?) of up to 3 amps would not damage it. OK what would? Higher voltages?

Could I provide infinite potential amperage without harming it?

 

[neil_w]

Thank you for trying.

"Current" where is 'current' relative to watts and amps?

Amps are the unit by which current is measured. 5 amps tells you how much current is flowing.

Watts are the unit by which power is measured. Watts = Volts * Amps

Specifically. this Weather Station will operate at 5V 600mA. (I'm sure a little more or less would still work.) I am being told here that providing it with a "potential" (am I using that word right?) of up to 3 amps would not damage it. OK what would? Higher voltages?

Potential also means voltage, so let's not use that word.

Let's say your weather station is a 8.33 ohm resistor. If I connect 5V to it, then using Ohm's Law again (V=IR) I see that I=.6A, or 600 mA. It doesn't matter if the power supply can supply infinite current (to answer your next question), only 600 mA will flow. And that's 5V * 0.6A = 3 Watts.

Again, the weather station is not a simple resistor, but for explanatory purposes we can consider it one for now.

 

[Brainlord Mesomorph]

And that's 5V * 0.6A = 3 Watts.

I did actually add that 3 watts up, and that the thing I'm buying is a 15 watt device. (and yes obviously I can put 23 watt CFL in a 100 watt lamp.)

So what would I have to to harm it? 6 ,7, 12 volts?

 

[Kelly]

I do understand most of "How electricity works" What I don't get when things go wrong and how to avoid it. If I stick my drinking straw into a city water main, the pressure would blow the back of my head off. When does that happen electrically?

Pressure is analogous to voltage. A city water main is high(ish) pressure, which is why you don't want to drink directly from it. Analagously, plugging your 5V weather station directly into a 12V supply would be bad.

Could I provide infinite potential amperage without harming it?

You could provide the capability of infinite amperage, without harming it, assuming it was at the right voltage. All of the AC outlets in my house are rated at 15amp or 20 amp capability, but I can plug a 0.5A wall wart into it with no problem. For a supply, the amperage merely states the maximum it is capable of supplying, not an amount that it will force through your device.

 

[Kelly]

I did actually add that 3 watts up, and that the thing I'm buying is a 15 watt device. (and yes obviously I can put 23 watt CFL in a 100 watt lamp.)

So what would I have to to harm it? 6 ,7, 12 volts?

It depends on the device, but yes, potentially anything great than 5V could harm it.

 

[Brainlord Mesomorph]

TYVM everybody, I've already ordered the parts

BTW that weather system is only $50 (reg $161) but it doesn't do wifi (not that I can get wifi at the park anyway).

 

[Brainlord Mesomorph]

Would it be right to say that an electrical circuit "pulls" amperage and "pushes" voltage?

i.e. you need to to provide more than your minimum amperage but less than your maximum voltage?

 

[Titan II]

Google is our friend. Here is one of hundreds of sites you may consider reading.

https://library.automationdirect.com/basic-electrical-theory/

 

[FredA]

Order this -- or 1/10th of this: Amazon 10-pack of buck regulators
Set to 5V .... sell the other 9

 

[Brainlord Mesomorph]

Google is our friend. Here is one of hundreds of sites you may consider reading.

https://library.automationdirect.com/basic-electrical-theory/

LOL
I'll try this.
I've wiki'ed things and watched 6 or 8 youtube vids today about this. None of which have been helpful.

 

[Brainlord Mesomorph]

Order this -- or 1/10th of this: Amazon 10-pack of buck regulators
Set to 5V .... sell the other 9

already bought this:
https://www.ebay.com/itm/224156807318

 

[FredA]

that will work

 

[neil_w]

Would it be right to say that an electrical circuit "pulls" amperage and "pushes" voltage?

Usually one would say a circuit *draws* current. A power supply “supplies” voltage and current.

i.e. you need to to provide more than your minimum amperage but less than your maximum voltage?

Yes for the current, but for voltage you typically need to provide within a specified range.

 

[Dan Griffing]

TL/DR: Its an electrical question; I have 12V,14A system and I want to power a 5V, 600mA accessory from it. I have found a 12V/5V DC-DC downstep, but it outputs 3 amps.
Can I use that if I add an appropriate resistor? Or what should I do?

Now, how does that have anything to do with rockets:

A couple of years ago I built this TOTALLY AWESOME launch controller (with a lot of help from this TRF thread: https://www.rocketryforum.com/threads/questions-about-my-diy-launch-controller.145459 Special Thanks to Voyager1 and OverTheTop)

It has 14AH of batteries, and a peak amperage that I have never been able to measure because it pops the 10 amp fuse. Now I gave it all that juice because I planned on powering other things from it. I’m building in an EggFinder LCD receiver (that will go in that blank space) and I’ll be adding USB DC Out for charging devices, etc.


Now I have bought this meteorological station:

The display should fit neatly in to lid of the launch controller

So, it comes with a 120VAC to 5VDC 600mA transformer.
I want to replace that with an aux power out from the launch controller. As I said above I have found this downstep at ebay
but its 3 amps and I need 600mA. So do I just add a resistor the to the output? And what resistor would that be?

Transformers only convert AC to AC voltages.

But there are many inexpensive automotive cigarette lighter USB converters costing less than $10 that provide up to 2 amps of current. These converters generally contain a voltage step-down regulator chip such as the ubiquitous LDO regulator. The only downside with LDO regulators is the heat and power dissipation involved, which is nearly 5 watts.

 

[jrap330]

Thanks



I've seen the plumbing analogy many times. Voltage is the diameter of the pipe?, amperage is the speed of the water in the pipe?, and watts is amount of water moving in the pipe. I even know W*V=A.

What I don't get is why in some situations electricity will fry a componamazoent and in others it will wait calmly in a battery.



(gasp) I never thought of that! I should build the Egg finder first, and just use it!
THANKS
[/QUOT

Sorry if I'm being thick, "I do nothing?" meaning "I can just use it as is"? or "I shouldn't do this at all?"

The 3 Amps isn't going to fry a 600mA device?

I'm still very vague on the concept of components "pulling" the power they consume from a circuit vs. batteries "pushing" power out and frying things, or whatever really happens.

nothing is push damn you built a controller without understanding basic ellectrical operation, therefore you should have done reading. the amperage is base your load, the resistance of the weather stations. I (amps) equals (E/R) ohm's law.

 

[jrap330]

you got that wrong volts is the pressure , resistance is the diameter of pipe and amps is the quantity of water flowing thru pipe. Squeeze your garden tube and water flows out in higher velocity/ pressure (voltage). Google basic electricity or get an intro book out of library..

 

[KilroySmith]

If I were you, I would put a Cigarette Lighter socket into that kick-*ss launch controller you built ( https://www.amazon.com/Cigarette-Motorcycle-Receptacle-Waterproof-ZHSMS/dp/B07H1MGWFN ), then I'd plug in any old USB charger like: https://www.amazon.com/AUKEY-Charger-Output-iPhone-Samsung/dp/B00M6QODH2 . Put a USB end on that weather station, and you're good to go. If you want to skip a step, installing one of these would simplify things a bit: (https://www.amazon.com/dp/B08FBY351F) but limit your ability to plug other things in.

 

[jrap330]

Pressure is analogous to voltage. A city water main is high(ish) pressure, which is why you don't want to drink directly from it. Analagously, plugging your 5V weather station directly into a 12V supply would be bad.



You could provide the capability of infinite amperage, without harming it, assuming it was at the right voltage. All of the AC outlets in my house are rated at 15amp or 20 amp capability, but I can plug a 0.5A wall wart into it with no problem. For a supply, the amperage merely states the maximum it is capable of supplying, not an amount that it will force through your device.

LOL
I'll try this.
I've wiki'ed things and watched 6 or 8 youtube vids today about this. None of which have been helpful.

Google find on Electrical theory, not bad but I can see it as confusing to someone who knows very little, I would have made in my simpler.

 

[KilroySmith]

The simple electricity/water analogy:

Voltage is like water pressure - if it's too high, your pipes burst (your electronics fry).
Resistance is like pipe size - as the pipe gets smaller, it has higher resistance to the flow of water, and less water can flow.
Current is like water flow - only as much water will flow out of a pipe as the resistance will allow. The city water main in front of your house may be capable of delivering 1000 gallons of water a minute, but due to the resistance of the small pipes leading into your house, your garden hose will only flow 5 gallons a minute. There's a problem if the city water main outside your house is too small - if it was only capable of flowing 0.1 gallons per minute, your 1 gallon per minute showerhead won't function correctly - you won't get a good shower.

For most things electrical, voltage is the primary concern - you don't want to blow up your stuff. As long as you keep the voltage appropriate, the device you have (whether a light bulb or a weather station) will work fine no matter how big a pipe (how much current) the thing it's connected to can supply as long as it's more than the device needs. If your weather station needs 600 ma, and you hook it up to a pipe that's only capable of 100 ma, you ain't gonna get a good shower (it's not going to work right/at all).

 

[jrap330]

The simple electricity/water analogy:

Voltage is like water pressure - if it's too high, your pipes burst (your electronics fry).
Resistance is like pipe size - as the pipe gets smaller, it has higher resistance to the flow of water, and less water can flow.
Current is like water flow - only as much water will flow out of a pipe as the resistance will allow. The city water main in front of your house may be capable of delivering 1000 gallons of water a minute, but due to the resistance of the small pipes leading into your house, your garden hose will only flow 5 gallons a minute. There's a problem if the city water main outside your house is too small - if it was only capable of flowing 0.1 gallons per minute, your 1 gallon per minute showerhead won't function correctly - you won't get a good shower.

For most things electrical, voltage is the primary concern - you don't want to blow up your stuff. As long as you keep the voltage appropriate, the device you have (whether a light bulb or a weather station) will work fine no matter how big a pipe (how much current) the thing it's connected to can supply as long as it's more than the device needs. If your weather station needs 600 ma, and you hook it up to a pipe that's only capable of 100 ma, you ain't gonna get a good shower (it's not going to work right/at all).

Great analogy.

 

[John Kemker]

I would recommend a buck converter. I used one to power the Raspberry PI for my 3D printer, coming off the 12V main supply. It's also known as a "DC-DC converter." Try this Amazon link for possibilities.