12v to 9v converter

[ghurd]

OK, I see.  Might be easier to reduce the TO-220 heat with a 3A diode because the voltage drop is more predictable.

The voltage drop in the resistor changes with current.

The 7809 needs about 2 or 2.5V extra to work properly, or 11.5V.  The resistor would throw things out of kilter with much of a load.

Smoke alarms are more in the half~1~2~3ma range.  Wild guess.

A 100ma drain would run a 9V Energizer dead in 5 hours.  And that takes the battery down to 4.8V at 21C.

G-

[Jeff]

Thanks again Ghurd!

BUT, like I said in my previous post, I removed the resistors I added AND connected it to my main 12v 700ah array. The reason I was reading such a low voltage was due to the much lower draw of the smoke alarm. I was figuring about 100ma, and you said "more like 1-3ma". Added cordless phone along with smoke alarm at 3am here. Still no problem, and voltage was 8.89 volts. "Feeling" the 7809 I could barely notice some warmth. So...at 11am (my "second" morning), I added the Life Alert box. Still no problem. Cordless phone: 250ma, Life Alert: also 250ma, smoke Alarm: negligable. The 7809 definitely felt warm to the touch, but not quite so hot you couldn't hold onto it.

Big surprise! Putting the handset on the cordless phone charger! I thought I popped the 7809. It got HOT. The smoke alarm beeped once, and I immediately unplugged the cordless phone & let the 7809 cool off. I haven't gotten around to checking output voltage, but at least the Life Alert & Smoke Alarm are still working.

So, for the time being: 1 unit for the Life Alert box & Smoke alarms, and 1 new unit for the phone! Glad I have the parts to make 4 like this!

With the way I had things hooked up & powered, that's still a savings of over 0.17 KwH per day! A little more, as I was running a wall-wart from my inverter to keep the "10v" battery charged up enough. The 10v battery being a 12v gel-cell with 1 dead cell. Gotta be much better all-around for the equipment I was running on that!

So, nothing lost except some extra power wasted, and more gained learning! Works out to: just over 0.177 KwH per DAY savings, not including conversion loss due to running wall-wart from inverter.

ps: decided to add a 1 amp fuse to this little circuit, especially if I'm giving them to other people!

[ghurd]

Cordless phones draw wildly different amounts of power.

Not only from one model to the next, but the same phone.

The power drawn is related to how charged the battery is.  Naturally it takes a lot more power if it is charging the internal battery than if the handset is not on the base.

Newer phones probably take less than older phones.  The phone I tinker with never takes an amp, but it takes enough to need a decent sized heat sink on the 7809.

The smoke alarm beeping may indicate the voltage fell, meaning the 7809 was either overheated or trying to supply over 1A.

[Clifford]

If you have individual cell batteries... (industrial/UPS batteries).

Then...

2.1V per cell.

String 4 cells together and you get 8.4V

String 5 cells together and you get 10.5V

And, of course depending on your charging/discharging the voltage could fluctuate a bit..  If the unbalanced load is small enough, your charging system won't even notice it.

However, I wonder if your smoke detectors would care about the fluctuations, or would start beeping at 8 to 8.4V.

Or..

You could find some NiMH D-Cells... (1.4 to 1.5 volts, charged).

6 of them would give you the equivalent of 1 alkaline battery.

You could probably make a small trickle solar charger.  It probably wouldn't take much.

Standard silicone cells will give you about 1/2V.

So 18-20 cells would give you about 9 volts.

Throw in a diode and you have a lifetime smoke detector (one hopes).

[Jeff]

You missed all my previous posts. I know it's a lot, but basically $0 to invest, these are for folks living entirely off-grid also with $0 income, and using 1-2 car batteries to power a couple little car lightbulbs, a Life Alert box, and maybe a smoke alarm. I'm making these little "converters" for them from recycled/junk parts like VCR's, Dish recivers, etc.

[Jeff]

Well, I got a good start on a second unit. Added an On/Off switch, a 1.5a fuse after that, and a 1amp fuse Coming out of the 9v side to the output jacks. I'd like to add a small LED, but I haven't found 1 yet that'll handle 12v OR 8v, the ones in the Harbor Fright Controllers checked out about 2 volts.

Here's some pics of the second container, and most of the "guts". This one is for the elderly guy I mentioned that his only electric is 2 car batteries. Every other day, a friend brings him the 1 battery he's been charging, and replaces it with the one he was using.

This time, I used something that the top could be screwed to almost anything/anywhere. The can with the guts inside can just be "popped" off if I need to do any more work on it.

First: the container...

Not the best quality camera, but you get the idea.

The "Guts"...

The metal piece on the left I got out of the old T-Bird I scavange stuff from. It has the 7809 mounted on a heat sink, and the two 10uf caps too. This screws to the bottom of the peanut jar. The Blue jack in the middle is a 1/4" jack (like used in guitar cords). This also mounts thru a hole in the bottom of the peanut jar & is labeled "12v IN". The two small black things on the right are 1/8" jacks, and also mount through holes in the bottom. These are labeled "9v OUT".

Not shown are the ON/OFF switch I've added, with a 1.5a fuse then feeding the 7809. The red wires twisted together coming from the 1/8" jacks & the yellow 9v output from the 7809 got the 1amp fuse added today. The switch and fuses proved all I could handle today.

I still have room to add the ON/OFF switch, and that's all on the bottom of a 12oz. peanut jar! Good thing, I've run out of solder!

So hopefully, I'll have a picture of the finished "Special Peanut Jar" in a few days.

[Jeff]

I finally finished 12v to 9v converter "version II" !!! Best of all, it works! And it runs my Life Alert box, cordless phone, and 2 smoke alarms!

I did add the ON/OFF switch, going to a 2a fuse. Thought I had a 1.5a, but couldn't find it. Also if I didn't say before, there's a 1amp fuse going from the 7809 9v output to the 1/8" phono jacks. I'm still using two 10uf caps. Ghurd suggested less, but I never found what he suggested. Of course, maybe some extended internet time would have turned up the labeling codes & made searching easier, but I'm very limited on internet time.

Here's the back, "working", or input/output side:

And here's how all the guts looked like packed in there. Inside of the black electrical tape with 2 red wires and 1 yellow (towards the edge at about the 4 o'clock position) is the fuse holder going to the 9v jacks. They were made to solder into a pc board, and I didn't want them touching anything.

And that's it! I'll leave it hooked up here tonight. If things check out OK tomorrow when I get up & around (around noon!), it's on it's way to the guy I mentioned who needs it desperately! Since he doesn't have a cordless phone, there should be even less worry of overheating.

Thanks again to all for helping this "little" project get working! Of course, it took me about 1 week for just this one, but maybe I can cut that down or get a "helper".

[Jeff]

It's off! As in: worked very well, warm to the point of barely keeping my finger on the 7809 with Cordless phone charging, Life Alert, and 2 smoke Alarms on it!

Since the guy it was going to doesn't even HAVE a cordless phone, I'd consider that safe. So... about 45 minutes ago, my friend 1/4 mile up the road who brought me a trailer-load of wood, a couple trailer axles & hubs, etc., picked up the 12v to 9v converter "version II" to take to the guy. I included an old-old guitar cord to plug into the input of the thing. Since it wasn't coax, it wasn't much good for using it from guitar to amp (makes too much noise). I also stripped the wires back far enough he could hook it up directly to the battery. The only thing he'll have to provide & hook up is the 1/8" phono jacks for 9v out, and wiring them into the guys Life Alert & smoke Alarms. Wish I had extra of those 1/8" male jacks, and could be there to help hook that up & eliminate any "boo-boo's" like reversing polarity and the like.

But all-in-all, I'm tickled you-know-what I got the chance to do some good around here where other powers-that-be don't do sh*!.

Thanks again all for helping me make this work. I'm going to have to take a break for about a week now & get ready for winter myself!

[Jeff]

I'm getting a humm on all the phone lines with this build. Doesn't seem to bother internet, but it does make my phone light come on on the Life alert system sometimes.

Refresh: using 2 caps 10uf 35 volts (smallest I could find without going under what Ghurd recommended). The 7809, and fused everything and that's it!

Any ideas? Put a choke in somewhere?

I double-checked to ground on batteries & getting 1 ohm (0.8 to 1.0). I know I shoulda used 7810's, but you never seem to find them in dumpster diving! They all use the darn 7809!

[Jeff]

Posting again since there were no comments/suggestions.

I'm getting a humm on all the phone lines with this build. Doesn't seem to bother internet, but it does make my phone light come on on the Life alert system sometimes.

Refresh: using 2 caps 10uf 35 volts (smallest I could find without going under what Ghurd recommended). The 7809, and fused everything and that's it!

Any ideas? Put a choke in somewhere?

I double-checked to ground on batteries & getting 1 ohm (0.8 to 1.0). I know I shoulda used 7810's, but you never seem to find them in dumpster diving! They all use the darn 7809!

Phone line voltage checks OK (50-52 volts AC). C'mon! Any suggestions?

[ghurd]

Double the cap values.  Or more.  I didn't figure you would have any problem.

This ain't NASA!

I don't see how a choke would help, but I'm not an RF guy.

[independent]

I know a guy who used to work at NASA as an aeronautical engineer.

He lives rurally and uses a lot of household chemicals to make photographic developers. If he can't easily get the right chemicals he will find a substitute at a hardware store, health food shop (Vitamin C makes for a good developing agent), or pool supply store.. What I am trying to say is he is never afraid to think outside the square and apply what he thinks might work (like alot of the excellent minds here do).

Sorry to take this off-topic..

[Jeff]

Thanks again ghurd! I have plenty of 47uf, 25v. I think I saw a few 20 or 22uf at 25v too.

Thought it was some kind of interference from some odd frequency and a choke was needed. Since I have the bigger caps, let's keep our fingers crossed! Lucky the folks who got the 2 "freebies" don't have cordless phones! But then, I got the same hum on the regular phone too. It stopped when I unplugged the new converter from the cordless. weird!

[wooferhound]

I have tried to power my cordless phone from my solar power too. I also have the same problem as you when I try to connect the phone to my RE Power. I discovered that all you have to do to make the hum is to ground the negative side of the line coming from the wall-wart and into the phone. The solution is to us a 12v to 9v "Converter" and not a regulator, but I have been having trouble finding one of these too.