12V to 5V conversion

My nephew is mucking about with home automation stuff and has wiring in his place for an alarm system. The original panel is still there with 12 volt power. He is asking me about using that to mount an iPad with 5 volt powe r. We found various adapters to go from the wiring to the connector needed (wire to USB A and USB to Lightning) for charging. Now I'm looking at 12 to 5 volt power converters. This one looks good, but there's no info on wh ether it is switching or linear.

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I'm thinking in such a small module it would have to be a switcher since it handles 3 amps. But then I'm also concerned about noise, so I'm going to recommend he add a couple of caps to the input and output. Anyone familiar with this product? Know of better ones?

The tablet will charge at 1 Amp, but operation often is significantly less. I'll remind him to find some software that will keep the charge level bel ow 75% to make the battery last.

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  Rick C. 

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Ricketty C
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is place for an alarm system. The original panel is still there with 12 vo lt power. He is asking me about using that to mount an iPad with 5 volt po wer. We found various adapters to go from the wiring to the connector need ed (wire to USB A and USB to Lightning) for charging. Now I'm looking at 1

2 to 5 volt power converters. This one looks good, but there's no info on whether it is switching or linear.

it handles 3 amps. But then I'm also concerned about noise, so I'm going t o recommend he add a couple of caps to the input and output. Anyone famili ar with this product? Know of better ones?

s. I'll remind him to find some software that will keep the charge level b elow 75% to make the battery last.

there is tons of modules like these on Ebay etc.

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or just go to a random electronics store and buy a USB car charger

Reply to
Lasse Langwadt Christensen

On Friday, July 10, 2020 at 6:30:12 PM UTC-4, Lasse Langwadt Christensen wr ote:

his place for an alarm system. The original panel is still there with 12 volt power. He is asking me about using that to mount an iPad with 5 volt power. We found various adapters to go from the wiring to the connector ne eded (wire to USB A and USB to Lightning) for charging. Now I'm looking at 12 to 5 volt power converters. This one looks good, but there's no info o n whether it is switching or linear.

e it handles 3 amps. But then I'm also concerned about noise, so I'm going to recommend he add a couple of caps to the input and output. Anyone fami liar with this product? Know of better ones?

ess. I'll remind him to find some software that will keep the charge level below 75% to make the battery last.

And plug it into what??? "Random" is not a selection criteria. I'm lookin g for something that will work well, not the usual crap sold on ebay or ali express. I bought a cheap USB wall charger once and when it would no longe r charge my flip phone (in spite of putting out 3.3 volts) it didn't even h ave a chip, just a single transistor. Looking for something of better qual ity and in a decent package which is what this unit clearly does, just not sure of the guts.

Looking for 12 volts wired to 5 volts either wired or USB A female. I supp ose even a microUSB output would do the job. I would like for it to be a s witcher and rated for at least 1.5 amps.

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Ricketty C

in his place for an alarm system. The original panel is still there with 1

2 volt power. He is asking me about using that to mount an iPad with 5 vol t power. We found various adapters to go from the wiring to the connector needed (wire to USB A and USB to Lightning) for charging. Now I'm looking at 12 to 5 volt power converters. This one looks good, but there's no info on whether it is switching or linear.

nce it handles 3 amps. But then I'm also concerned about noise, so I'm goi ng to recommend he add a couple of caps to the input and output. Anyone fa miliar with this product? Know of better ones?

less. I'll remind him to find some software that will keep the charge lev el below 75% to make the battery last.

ing for something that will work well, not the usual crap sold on ebay or a liexpress. I bought a cheap USB wall charger once and when it would no lon ger charge my flip phone (in spite of putting out 3.3 volts) it didn't even have a chip, just a single transistor. Looking for something of better qu ality and in a decent package which is what this unit clearly does, just no t sure of the guts.

ppose even a microUSB output would do the job. I would like for it to be a switcher and rated for at least 1.5 amps.

and that is what you from a USB charger meant to plug into a cars cigarette lighter, it'll even have the pins in the required state to make a phone/ta blet recognise it as a charger

Reply to
Lasse Langwadt Christensen

In that size it's switching. ther's no way that plastic pack could dissipate 21W

I'm a fan of the "MH" branded open XL4015 modules.

They cost under two bucks and at 2A load they run just barely warm.

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seeing as the supply is 12V something like Mini 360 (max input voltage

17V) would be an option too.

under a buck,

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under half a buck at qty 10.

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But with Aliexpress, Ebay, Banggood, Amazon, etc you're buying from a reseller who may not understand their wares.

These guys are good and price their stuff in the same ballpark:

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This module has solder jumpers for several convenient preset voltages after you cut the track to the potentometer

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I'd de-rate it to 1.5A continuous, 3A surge.

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  Jasen.
Reply to
Jasen Betts

On Friday, July 10, 2020 at 6:30:12 PM UTC-4, Lasse Langwadt Christensen wr ote:

his place for an alarm system. The original panel is still there with 12 volt power. He is asking me about using that to mount an iPad with 5 volt power. We found various adapters to go from the wiring to the connector ne eded (wire to USB A and USB to Lightning) for charging. Now I'm looking at 12 to 5 volt power converters. This one looks good, but there's no info o n whether it is switching or linear.

e it handles 3 amps. But then I'm also concerned about noise, so I'm going to recommend he add a couple of caps to the input and output. Anyone fami liar with this product? Know of better ones?

ess. I'll remind him to find some software that will keep the charge level below 75% to make the battery last.

Grin. There's also these three terminal (switching) voltage regulators... Not 3 amps though.

George H.

Reply to
George Herold

his place for an alarm system. The original panel is still there with 12 volt power. He is asking me about using that to mount an iPad with 5 volt power. We found various adapters to go from the wiring to the connector ne eded (wire to USB A and USB to Lightning) for charging. Now I'm looking at 12 to 5 volt power converters. This one looks good, but there's no info o n whether it is switching or linear.

ess.

elow 75% to make the battery last.

eller

er you cut the track to the potentometer

the boards are fine, but be sure to check the output voltage, the presents never match

Reply to
Lasse Langwadt Christensen

is place for an alarm system. The original panel is still there with 12 vo lt power. He is asking me about using that to mount an iPad with 5 volt po wer. We found various adapters...

Would you consider a vehicle-power USB charger? Monoprice is usually a good source, and you get a choice of USB-A or USB-C (or both). And, rea l charging logic (required for the higher USB-C powers) beats a raw converter module.

Reply to
whit3rd

On Friday, July 10, 2020 at 7:04:18 PM UTC-4, Lasse Langwadt Christensen wr ote:

g in his place for an alarm system. The original panel is still there with 12 volt power. He is asking me about using that to mount an iPad with 5 v olt power. We found various adapters to go from the wiring to the connecto r needed (wire to USB A and USB to Lightning) for charging. Now I'm lookin g at 12 to 5 volt power converters. This one looks good, but there's no in fo on whether it is switching or linear.

since it handles 3 amps. But then I'm also concerned about noise, so I'm g oing to recommend he add a couple of caps to the input and output. Anyone familiar with this product? Know of better ones?

ly less. I'll remind him to find some software that will keep the charge l evel below 75% to make the battery last.

oking for something that will work well, not the usual crap sold on ebay or aliexpress. I bought a cheap USB wall charger once and when it would no l onger charge my flip phone (in spite of putting out 3.3 volts) it didn't ev en have a chip, just a single transistor. Looking for something of better quality and in a decent package which is what this unit clearly does, just not sure of the guts.

suppose even a microUSB output would do the job. I would like for it to be a switcher and rated for at least 1.5 amps.

te lighter, it'll even have the pins in the required state to make a phone/ tablet recognise it as a charger

It is a completely wrong form factor. It would need to be torn apart and r ebuilt. Neither the person using this nor myself want to bother with that when the perfect form factor is available.

Then there is the tiny issue that 95% of the stuff for phone charging is co mplete crap. I'm always scared to use much of it until it has been thoroug hly tested. Not worth the bother for this. That's why I am asking for rec ommendations. To avoid the crap products.

Thanks for the idea anyway.

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  Rick C. 

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Reply to
Ricketty C

his place for an alarm system. The original panel is still there with 12 volt power. He is asking me about using that to mount an iPad with 5 volt power. We found various adapters to go from the wiring to the connector ne eded (wire to USB A and USB to Lightning) for charging. Now I'm looking at 12 to 5 volt power converters. This one looks good, but there's no info o n whether it is switching or linear.

What about EMI? My nephew would need to package this since it is going ins ide a wall box. I guess the better place for this is not the end outlet bo x, but the main box which is probably over a foot square and can probably d issipate some heat. The odd thing is the transformer that powers this is i n the attic while the panel is somewhere else. Why would they put the powe r source in the attic???

ess.

elow 75% to make the battery last.

eller

er you cut the track to the potentometer

If you recommend these guys... but do they make any of this stuff or just resell it? This one is interesting as it has the USB connector built in.

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They talk about a 1.5 amp input fuse, I see something labeled R10. But tha t sounds like a 0.1 ohm resistor to me. The output protected from over vol tage by a TVS. How exactly would that work? Seems like the TVS would blow and then your tablet would blow.

I haven't talked with my nephew about electronics since he was 8 and wanted me to help him build a robot. lol He's a PA in Houston now and works at Children's hospital where things are heating up from the virus. This modul e would require soldering. If he hasn't done that before, he can learn now . Still, I just have no idea if these devices can be trusted. Then there is no way to mount it other than tape.

I also know nothing about what it takes to get the phone to draw an amp whi le charging.

I was going to add some USB power to the ash tray in my truck, but someone stole my truck and I may not replace it. The car already has USB power con nectors.

I will book mark these guys. Thanks.

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  Rick C. 

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Reply to
Ricketty C

his place for an alarm system. The original panel is still there with 12 volt power. He is asking me about using that to mount an iPad with 5 volt power. We found various adapters...

eal

er module.

The form factor is wrong. There's no cigarette lighter socket... I mean po wer interface socket to plug it into. I'm looking for a box with the right words on the outside, the right electronics on the inside and four wires s ticking out or terminals for connecting wires.

Isn't that what you would want to shove in an electrical box in your house? I just don't want to recommend a 70 cent gadget if a $10 gadget is more l ikely to work.

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  Rick C. 

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Ricketty C

power interface socket to plug it into. I'm looking for a box with the rig ht words on the outside, the right electronics on the inside and four wires sticking out or terminals for connecting wires.

OK, those can be had as a car- motorcycle-upgrade item; howzabout this?

e? I just don't want to recommend a 70 cent gadget if a $10 gadget is more likely to work.

The negotiation of power for anything other than 100 mA and/or 500 mA migh t be a difficulty with a modern tablet; they just have to talk to the socket (an d I'm not totally sure how) before the real power flow starts. Lightning/Thunderbolt and USB-3.1 should accept a goodly amount of power from the right kind of socket, but I've also seen cellphones that wouldn't charge from a charger that lacked the right password (or resistor) .

Modern USB-C 3.1 chargers aren't exactly 5V, even. If they're happy with the handshake, you can get 20V, 5A.

Reply to
whit3rd
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Reply to
TTman

I haven't noticed any EMI, but I haven't been looking. they run at hundereds of kiloherts so there probably are harmonics in the AM broadcast band. the MLCCs on input and output probably help with that more than the solid electrolytic capacitors do.

Many of their other modules have their logo in the silkscreen. I don't know if they have a dedicatred factory. I suspect their modules may be manufactured under contract. It looks like the one in the photo has the sticker over the logo.

It might be that resistor, I don't know how to tell a fireproof fusible resistor from a regular one without doing a destructive test.

there's something going on there as they've put an undersized part on those pads.

Epoxy works too. or heatshrink it in place. or a cable tie between the socket and the inductor... it may have been designed for a special enclosure

There is that. Apple had a different charger detection scheme to android. this module has the data pins shorted together, I don't know what an iPad will make of that. still a fixed tablet will probably be fine with a 500mA charger as it will spend most of its time attached to a working charger.

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  Jasen.
Reply to
Jasen Betts

The transformer is in the attic to keep it from being disconnected. Either accidently, or on purpose. A fact that was difficult to teach to new instal lers. "But the electricians installed an outlet right here!" Some friends f actory was broken into. They cut the wires off every transformer to try to kill the alarm. They even pulled the electric meter before they gave up and fled.

Reply to
Michael Terrell

Leaded flameproof resistors had a light blue body, when I was using them.

Reply to
Michael Terrell

r accidently, or on purpose. A fact that was difficult to teach to new inst allers. "But the electricians installed an outlet right here!" Some friends factory was broken into. They cut the wires off every transformer to try t o kill the alarm. They even pulled the electric meter before they gave up a nd fled.

The alarm has a battery as do nearly all such devices. Cutting the power c able is still easy since it has to come from the attic to the alarm panel. Nothing about putting the power transformer in the attic makes it more tam per resistant. Nothing!

Having the transformer in the attic makes it awkward to service. I suppose it might be less likely to be unplugged when someone plugs in the vacuum c leaner, but a sounder in the cabinet would remind them to put it back. Tha t's the typical way to alert people the power has been cut.

The main reason I am not telling my nephew to ditch the alarm circuit board is because it contains a 12 volt UPS. That's worth keeping.

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  Rick C. 

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Reply to
Ricketty C

It was standard practice when i taught people to install alarms, in the '70s. What makes you think that a janitorial service cares what they leave unplugged?

Reply to
Michael Terrell

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