Author Topic: 12v to 9v converter (Read 16214 times)

Jeff · « **on:** October 12, 2008, 06:37:28 PM »

I am now in the process of having to build at least 8, preferably 12, 12 volt to 9v converters. I've come up with a schematic (pic included), but my question is: What do I replace Q1 with (ECG184 or NTE184) to make it more "robust".

My "helpers" and I have come up with most of the parts excepting Q1 of course. Even enclosures, heat sinks, and fuse holders!

We would like to have a 3 amp and 5 amp version, but whatever is more available or cheaper, this can be changed to 2 amp and 4 amp versions.

The "include picture" option did not show up! So...here's the URL here.

Heres the photo:

Tom

Jeff · « **Reply #1 on:** October 12, 2008, 01:01:18 PM »

Thanks Tom!

Jeff · « **Reply #2 on:** October 12, 2008, 01:09:30 PM »

Sorry, guess I could have included the parts list! DUH!

R1 = 560 ohm

C1 = 1000uF/40V, Electrolytic

C2 = 10uF/25V, Electrolytic

C3 = 330nF, Ceramic

Z1 = 9.1V, 1watt zener

Q1 = ECG184, NTE184

I could replce diode Z1 with 10V and R1 with a 1Kilo ohm potentiometer. And may even have to do that on a few due to customers with "unknowns" and/or available parts, but I hope it isn't the norm. I only have enough for 2 of these, and still looking for more 9.1v zener's. I know...google or Radio Shock, but dial-up is sooo slow! Geez! I need a 45w zener for a 5 amp output!?!?

scoraigwind · « **Reply #3 on:** October 12, 2008, 01:11:13 PM »

Why not just buy a chip that does this, for example KA278R09CTU-ND?

Flux · « **Reply #4 on:** October 12, 2008, 01:37:24 PM »

If you want to go the discrete route then use something like a TIP41 for the pass transistor. You will need to heatsink it reasonably well for 3A.

You will loose about .6v so with 9.1v zener you will be low on 9v but probably ok. 10v zener may be a better choice.

I go with Hugh, far simpler to buy a regulator chip with over temperature and short circuit protection.

Flux

Jeff · « **Reply #5 on:** October 12, 2008, 01:51:44 PM »

OMG! Thanks all!

Right now, I have several elderly or disabled folks (one of them me!) running 2 smoke alarms, a cordless phone, and a life-alert box, or more! from old, half-dead car batteries!

Not only makes me proud & boastful of everyone here, but glad I came up with enough details to be almost non-newbie!

BTW, anyone who asks how I can manage on $0 income & still have electric for everything, I point them here!

now...where's the "smiley" icon???

Jeff · « **Reply #6 on:** October 12, 2008, 01:53:25 PM »

ps.: no need to answer that last comment! The thanks were almost enough!

ghurd · « **Reply #7 on:** October 12, 2008, 03:57:12 PM »

Not great info, but why lose 1/10th of a watt in conversion for an item that only uses 1/50th of a watt?

My smoke alarms run 2~3 years on a 9V alkaline?

No hope of powering an IC on that kind of power.

"my" cordless phone uses less power (24/7/365 average) than a Datel Murata "78xxSR" wastes with no-load.

But it is easy and worth a look.

G-

independent · « **Reply #8 on:** October 12, 2008, 04:52:55 PM »

Hello all. Another way to skin a cat!

I use rechargeables for everything. Most get charged up off my 5w panel daisy chained to an SLA battery in the sun (while my main power sourse is being built ;-). In Silicon chip (Aussie electronics mag) some years ago there was this fantastic circuit that adapts a standard nokia cellphone car adapter to a variable voltage constant current power supply. In fact most of these car adapters use this same MC34063 ICs for voltage regulation. Aha, they all use this chip because it can provide a current regulated output of between 10-2vdc by substituting two resistors with 5k pot. The trick is finding the two resistors. Once that's done it's plain sailing, or soldering.. I've made a few different chargers for things, the two main ones I use now are a 9v NiMh charger and a cordless screwdriver charger which has had it's old cells swapped out for some new ones put back into service.

If the interest is there, I'll try and get something online sooner rather than later. Anyway, it's a great cheap source of self regulating current limited battery chargers as these things can be bought really cheaply (I think N Americans call them "dollar shops" ;-) Not all car chargers are the same quality, the "dollar shop" ones can be a real pain to work on with circuit boards holding 9-10 components about 1x2cm in size. I prefer to get the ones in 2nd hand shops that are discarded, but "genuine" brand name chargers. The components on those are usually much better and the circuit board will be easier to work (solder your 5k pot to).

Anyway, not all rechargeable 9v batteries are same either. Most are 7.2v and 8.4v, a very few are 9.6v. I believe they are usually made with AAAAA 1.2v NiCd or NiMh cells.

Really efficient charger, cheap to make, also can charge 4xAA cells and anything else in that 2-10vdc range. I even thought, seeing as they're current limited (I think to 100mA or so) they would make a cheap efficient constant current LED circuit.

Jeff · « **Reply #9 on:** October 13, 2008, 09:54:58 AM »

I know, it was easy to overlook after going back over it myself. But in another post, I mentioned "these folks have NO power, except a car battery or two!"

What would they plug the "wall-wart" into? Most of them have $0$ income, and Food Stamps won't allow them to buy things like toilet paper, feminine products, or even 9v batteries for a smoke alarm!

Letting someone else "use" their Food Stamp card & then having that person give them "real" money to buy those necessities is illegal! Even for a ridiculouse amount like $5-10!

Someone(s), in other words government/state officials are so afraid people might use this method for things like tobacco or alcohol, they've forbidden Everything not considered nutritional from being bought using Food Stamps.

I know, it's done, but every week or so you see a small posting of "12 people caught mis-using Food Stamps" in the local paper.

I eventually end up with so many documents "tied" together, I have trouble keeping up with them!

sorry, I'll get off the RANT box now.

And I apologize in advance to Ghurd: he only reminded me of why I was doing this in the first place.

Thanks again to all the excellent suggestions!

ghurd · « **Reply #10 on:** October 13, 2008, 10:13:19 AM »

I meant why build a 2 to 4A regulator, if the system can be split up into smaller parts.

Like if the cordless phone uses 9VDC, then just use a 7809. It would be a lot less power losses. And a lot cheaper.

Some cordless phones and answering machines run from a 12VAC wall wart, then go into a bridge inside the phone. Some of those run fine straight off a 12V battery. Some need AC to work.

Up to the owner if they want to risk it, but I haven't blown one up. Yet.

G-

Jeff · « **Reply #11 on:** October 13, 2008, 10:44:03 AM »

Independant: Thanks for the suggestion of the MC34063 ICs for voltage regulation!

I think if you read my "reply" to Ghurd above, you'll understand why I'm not going the rechargeable AA route. The cost of 8 of those here is about $16-18, and would need extras for when the first batch goes dead.

Ghurd: Ahhhh! Thanks again! GREAT idea! Consider it "copy & pasted" in several places, and I even tried to write it down!

I know about running some of those things directly from 12v, or taking a peek inside just to see if it goes to a bridge, and then testing the output! Right now, I'm using a couple 12v batteries with a dead cell which hold 10v at best. I did fry a 9v cordless phone recently running it on 12v though. A friend gave me a box FULL of old cordless phones!

jimjjnn · « **Reply #12 on:** October 13, 2008, 11:20:12 AM »

The 78XX series of regulators are great .

You can build multiple outputs with a number of them for various voltages in one box.

You only need one transformer, bridge rectifier, Filter caps, and multiple 78XX regulators plus a few minor components.

Also can do same w/o transformers and brige if you have a steady and reliable DC source.

independent · « **Reply #13 on:** October 13, 2008, 01:05:42 PM »

I was suggesting rechargeable 9v batteries not AAs (although you can charge these up too in this hacked car cellphone charger). The cost to make a 9v charger would be essentially free. Chargers, 5k pots, and 9v connectors are all easily found in discarded devices. Well anyway, all the bits for my chargers were essentially free.

The only cost would then be rechargeable 9v batteries. I have 9v (actually 8.4v) NiMh batteries in our smoke alarms. NiMh batteries don't handle as many recharges as Nicads so maybe that would be the best way to go. That said, I've had our 9v NiMh batteries for years now and they last over half a year in the smoke alarms (plus whatever other duties I need them to do).

So, 9v Nicads (usually 7.2v) are not that common here, but I have found some for cheap. Well, not that much more expensive than normal 9v batteries ($4US each). Maybe you could organise a bulk buy for your friends from an electrical supply house (mail order), make up a few chargers and spread them around?

The only potential problem is to check that 7.2v Nicads work properly in smoke alarms. Their charged voltage is over 9v so they should be fine, worth checking anyhow.

I consider smoke alarms to be an essential household item, one save my Grandmother's life even though she was deaf as a doorknob. This would be the safest way to keep them working.

Airstream · « **Reply #14 on:** October 13, 2008, 01:45:13 PM »

Glad you are using smoke detectors but there is a problem with using rechargables - unless it is in a line powered unit that has a specific 9V trickle charger built in.

Courtesy of Wikipedia (http://en.wikipedia.org/wiki/Nickel_metal_hydride_battery)

NiMH historically had a somewhat higher self-discharge rate (equivalent to internal leakage) than NiCd in the past. However, this is no longer the case. The self-discharge is 5-10% on the first day, and stabilizes around 0.5-1% per day at room temperature. This is not a problem in the short term, but makes them unsuitable for many light-duty uses, such as clocks, remote controls or safety devices, where the battery would normally be expected to last many months or years. The rate is strongly affected by the temperature at which the batteries are stored with cooler storage temperatures leading to slower discharge rate and longer battery life.

A new type of nickel-metal hydride battery was introduced in 2005 that reduces self-discharge and, therefore, lengthens shelf life. By using a new separator, manufacturers claim the batteries retain 70 to 85% of their capacity after one year when stored at 20 degrees Celsius (68F). These cells are marketed as "ready-to-use" or "pre-charged" rechargeables. Besides the longer shelf life, they are otherwise similar to normal NiMH batteries of equivalent capacity and can be charged in typical NiMH chargers.

Low self discharge batteries have lower capacity than standard NiMH batteries. The highest capacity low self discharge batteries have 2000-2100mAh and 850mAh capacities for AA and AAA batteries, respectively, compared to 2800mAh and 1000mAh for standard AA and AAA batteries. However, after only a few weeks of storage, the retained capacity of low self discharge batteries often exceeds that of traditional NiMH batteries of higher capacity.

Airstream · « **Reply #15 on:** October 13, 2008, 01:55:34 PM »

Missed idea, hit 'post' a little too fast...

I'd JUST seen the 'pre-charged' AA's when I bought ones to replace the 2003 vintage batteries I was using in my 2003 vintage digital camera & wondered what the advatage was; guess Wikipedia cleared that up! I still feel uncomfortable trusting smoke alarms to a rechargeable..

I personally use the 10-year lithiums made expressly for safety-related devices; if they are going to go bad they usually fail within a week or two of installing and occasionally go on sale for a decent price.

independent · « **Reply #16 on:** October 14, 2008, 12:28:52 AM »

My smoke detectors work fine with NiMh although I will be using Nicads soon. I check their voltages regularly and have no problems with them at all discharging too fast.

independent · « **Reply #17 on:** October 14, 2008, 12:31:42 AM »

..and check to see they are working with the little "test" button ;-)

Jeff · « **Reply #18 on:** October 14, 2008, 02:59:01 PM »

Like I mentioned before, these things are for folks with $0 income! Currently, churches are their only hope of getting things like this, toilet paper, etc.

Since many don't have A/C, they commonly have to deal with 90 degree plus inside temps! A 12v fan is a luxury for them!

So... the "barter system" has come back into vogue in a BIG way!

If I can make several of these types of things (from recycled/discarded electronic devices) to help as many as possible, it helps more than just that person. It also helps the churches, who are barely able to keep those people in batteries and toilet paper! Let alone paying a power bill from the local electric co-op.

For example: I have 2-3 friends that save their aluminum cans for me. Also, whenever I am able to "cruise" the local back roads in my wheelchair, I collect them. Usually within a month to 6 weeks, a friend takes them to the recycling center & cashes them in. He then pays my $8 per month phone bill for me!

I am on Life Alert. This requires an active phone line, and uses a 9v "wall-wart". HOWEVER, local Social Services, electric company, help centers, cannot and DO NOT keep up. I'm not allowed to even make the $8 to pay a monthly phone bill, let alone the average $20-$25 per month to keep my electric on, or keep my wheelchair charged! I know there may be plenty of comments on this, and suggestions, but basically "our system is broke, or not able to keep up". I feel very lucky I'm able to have the luxuries of a small solar powered system, and can use a computer, and have found two internet providers with 10 hours each per month free!

In fact, this took too long. I found 4 7809's in fried H.F. controllers! I had a question on wiring them up, but my times up. Hopefully tomorrow!

Thanks to all again!

and yet again, having problems uploading picture. File name not shown in list.

http://www.otherpower.com/images/scimages/9063/7809_reg.jpg

TomW · « **Reply #19 on:** October 14, 2008, 04:29:14 PM »

Jeff · « **Reply #20 on:** October 15, 2008, 10:25:06 AM »

Thanks again, Tom!

Now! Question is: I've seen 2 different pin-outs in the 7809 chip.

Facing the front of the chip in the photo. Left to right. 1: attach to resistor approx. 370 ohms (or should that be a cap?) 2: +9.1v out 3: +12v in

I'm assuming the other end of the resistor goes to ground.

In the photo is the 7809 chip from the "famous" Harbor Fright controller box. The red lead on the left (1) appeared to come from the hot + side of the 12v outlets. Center Black (2) to the hot + on the 9v outlets and on to the 6v and 3v outlets. The last Red lead (3) went to the solar controller board, and I couldn't trace it from there.

I know it's probably a simple matter for one of "the Guru's" like Ghurd, or Commanda. But I'm having a hard time getting (finding) something so simple in a reasonable amount of time. In other words, I can't stay online 4-5 hours searching the internet for something that could be explained/done in 10-15minutes.

Hopefully, the first (top) guess is close. And the wiring in the second example is just "The Harbor Frightmare".

ghurd · « **Reply #21 on:** October 15, 2008, 10:32:58 AM »

Common configuration.

Metal tab on the table, legs pointing to you, letters are right side up and facing you.

Left pin is Vin (12 to 37V), center is negative, right is 9V out.

Small cap from Vin to negative, and another from 9V out to negative.

G-

Jeff · « **Reply #22 on:** October 15, 2008, 11:41:18 AM »

YEEEHAAAA! Thanks Ghurd! Checking w/multimeter, I did notice center was to base (ground).

Thank you! Thank you! Thank you!

Jeff · « **Reply #23 on:** October 16, 2008, 02:02:57 PM »

Got one working! I'm using a 1000uf cap 16WV on each side. Funny, never seen them labeled "WV", just volts. Maybe it's made in West Virginia! LOL

Thanks again all, and especially to Ghurd!

I wonder how many amps the 9v side can draw without smoking? AND, how many amps if I use Two 7809's in paralell. I have the 7809's on a cute little heat sink.

The first one is installed in a dead cordless phone shell (the hand unit). I got lazy when I noticed I could use some of the empty holes for in-out jacks! LOL

Another good chapter in this: I have enough to make Two like this! One I use, the other is for sale/barter for the folks around these parts. YEEEHAAAA This could get me 6 months of toilet paper, or pay a month's phone bill!

Uhhhh....Did I say thanks?!?!?

Jeff · « **Reply #24 on:** October 16, 2008, 02:15:39 PM »

added: I forgot to mention, I do have several smaller caps. 470 & 100uf @ 25-50 volts. I can probably come up with other/more if a different size is recommended for as much as a 2amp draw @ 9v. Suggestions for that, and a 3-4amp version appreciated.

Fieldlines Rules! And I've already told some folks not only about WHERE I got the schematics & details for this little project, but whenever they ask about my home-brewed power system, they get directed here too. Sooo...if you've got an over-flow of visitors lately, you can blame part of it on me!

(Smiley Icon giving the "rasberry" here)

ghurd · « **Reply #25 on:** October 16, 2008, 02:35:01 PM »

TO-220 78XX are often rated for 1A, IF they have a big heatsink.

Ratings vary from 0.5 to 3A.

Watts of heat = (Vin - Vout) x Amps.

So (14Vin - 9Vout) x 1A = 5V x 1A = 5 watts of heat (and that is a Lot for something TO-220 size). I like to keep TO-220s below 1W of heat.

They can Not be paralleled without a bit more parts & effort, and greater understanding, IMHO. Not a dig, just it can get complicated.

It is possible to add bypass transistors to increase the current capacity, though I don't care to bother with that route myself.

You missed part about "Small cap". 1000uF may cause some problems, not sure.

Think 10 to 47uF.

Be careful of unknown caps. Use 16V min. 25V would be better.

G-

Jeff · « **Reply #26 on:** October 16, 2008, 03:05:25 PM »

Again, many thanks Ghurd! Whew! Glad I only tried this on a 200mA cordless phone!

And yet again... Thanks, I do have enough 10-47uf caps to make a couple of these!

I do have a schematic to bump up the amperage demand, and yes, it does get more complicated. I could do it, but trying as I am for strictly recycled parts, buying even the one extra chip I DON'T have borders on the cost vs. value for the application. Application being all mentioned and re-mentioned in previous posts above.

Jeff · « **Reply #27 on:** October 19, 2008, 11:49:33 AM »

The latest:

Thanks to Ghurd, I did change the two caps to some 47uf 25v ones. I had an old junk Dish reciever that had a LOT of those in it! The 16v ones, the 25v, even found some 10uf 35 or 50 volt (CRS - can't remember ....).

The schematic picture I first posted IS for a "ramped-up" version supposedly capable of handling 1.5 amps. My problem was I didn't have anything comparable to the ECG184 chip.

I could always add one of those big resistors I got from the Marshall/Scholz power soak. An 8w one (about 3/8inch square 1 - 1/4inch long) does bring down the voltage almost 1 volt. Reasonable considering I tested it on a battery with barely a 12v charge, 1.7 amp fan, and still tested at 11.2 volts. I know it adds to the load, but the Life Alert box or the smoke alarm both draw about 200ma at 9v. That's 1.8 watts for one or 3.6 for both. Add in the 8 watt resistor, and an 11.6 watt draw on my large (700Ah) battery array isn't much problem. Now someone with a single car battery...most likely a different story!

That's still equal or even less than the wattage I'm drawing from a Wall-wart that runs from my inverter only when the fridge comes on. This is what is keeping my "10v battery" charged. AND, it cuts down the voltage differential the 7809 has to deal with. Thus cutting down heat. I think I read somewhere the 7809 needs 11v in minimum to operate correctly, that's why I tested & chose the 8w resistor for my own 9v converter.

I still think it would be best to make one for each device (like Ghurd suggested) without the 8w resistor for now. This would be on ones I make for other folks around here. Maybe soon I'll find the ECG184 or something similar to make a few that can handle 1-2amps easily, and not draw so much for those with a single battery.

With the "barter system" as it is around here. Those that help others WILL be remembered. In other words: You reap what you sow!

And that is exactly how I have made it here these last 6 years!

Adding more in my "New Wheelchair post soon!"

ghurd · « **Reply #28 on:** October 19, 2008, 12:40:15 PM »

The caps can be about 10X smaller. My bad.

About 0.33uf on the Input side to ground, 0.05uF on the Output side to ground is usually enough.

If you seek efficiency, designs with 8W resistors is usually a sign it wastes nearly 8W!!!

Part numbers starting with ECG or NTE come at a cost.

G-

Jeff · « **Reply #29 on:** October 19, 2008, 04:31:48 PM »

Ghurd,

I hate to keep saying "thanks", but you know how Momma's are. It's been drilled in with an impact wrench, and Dad enforce my oversite with a belt!

The schematic in the first photo, like I said, was for a souped-up config that would stand up to 1.5 amps w/no problem.

Making a second model, I used 10uf 25v on both sides. With a smoke alarm attached, it read 8.82 volts. I replaced the 8 ohm resistor with a 6 ohm and got the same ouput voltage. I was planning on removing it entirely until I read your post.

Yes, it's just watts "wasted", at the cost of protecting the few 7809's I have. Better safe than sorry.

So, would the change to 0.33uf on the Input side to ground, 0.05uF on the Output side get the voltage up a little? AND/OR remove the 6 ohm resistor alltogether? I haven't checked the draw - amps of the smoke alarm, but the Life Alert system used a 300ma 9v Wall-Wart. Would Love to have 1 model ASAP that would handle both and possibly a second smoke alarm.

thanks again!

jp

Jeff · « **Reply #30 on:** October 20, 2008, 03:06:05 PM »

I have removed the 8 ohm resistor. Volts are still 8.81-8.82. This is even with it connected to my big battery array, which holds fairly steady at 13.0 to 13.18 volts. I haven't located the lower uf caps Ghurd mentioned. I've only looked for 10-15 minutes though, as it still seems to be working fine with no noticeable heat buildup. The old "carefully touch the parts" method, and like I said, no noticeable heat buildup. Since I do have the parts to have two, I will connect the cordless phone in with the smoke alarm tonight I hope. Like most everthing else I do lately, it's one small step at a time.

Any further explanation of why the smaller caps, and what will happen if I run with the 10uf 25v ones on each side?

Is this what is causing the lower voltage reading, or why it's often suggested to go to a 7810, or 10v regulator? If so, I'm kinda out of luck there, as I haven't seen ANY 10v regulators in the junk boards/equipment I've been scavenging. LOTS of 7812's, but no 7810's. May be Ghurd's thinking of the smaller type (small cylinder with a flat on one side) & I'm over-looking them, and also why he is cautioning me (very wisely) of not trying to draw too many amps from them!?

After repeated correcting of my typos, and using the preview button, I realized I have the parts for FOUR of these 12v - 9v converters! That's using the 10uf caps though. But, my second Harbor Fright controller has two 7809's in it! Since I'm in no danger of over-charging my batteries, all I need is a GOOD blocking diode to protect my H.F. panels!

ghurd · « **Reply #31 on:** October 20, 2008, 04:01:36 PM »

I am confused about the 6 and 8 ohm resistors, and where or why they are connected.

All it takes is a 7809 and 2 small caps. That's it.

The caps are like shock absorbers. They will not effect the output voltage with the equipment you have to measure it.

The output of 8.81V is withing about 2%, so plenty close enough.

The IC will not get hot with no load. It only draws about 0.0025A (0.033W) with no load. It will start making some "heat" at about 0.125A of load.

The small cylinder type 7809s are TO-92 size. They are only rated 50 to 100mA. Not worth the effort of trying to get them out.

G-

Jeff · « **Reply #32 on:** October 20, 2008, 05:01:56 PM »

Ghurd,

You said Watts of heat = (Vin - Vout) x Amps.

So (14Vin - 9Vout) x 1A = 5V x 1A = 5 watts of heat (and that is a Lot for something TO-220 size). I like to keep TO-220s below 1W of heat.

So, I added the 6-8 ohms resistor from the pos. side of the battery to the 12v in side of the 7809, just to reduce the voltage going into the 7809 and hopefully the heat. Kind of a moot point now though.

Also, I DID mention the 9v out was connected to a smoke alarm. Also, I didn't measure what that (smoke alarm) was drawing, but I assumed it's in the 100-200ma range.

News:

Author Topic: 12v to 9v converter (Read 16214 times)