Author Topic: 12 Volt Answering Machines  (Read 11789 times)

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armadillo

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12 Volt Answering Machines
« on: July 28, 2015, 04:23:33 PM »
Does anyone else have their answering machine hooked up to DC?   I had been using a Radio Shack answering machine for 5 years, the wall wart says 9VDC and 12 volts DC seems close enough. It worked for years anyway.
After a lightning strike a few months back, that answering machine failed and I got another 9 VDC unit off of ebay, and another and another.  The last 3 three worked OK for a couple days and then caused static on the phone line and when someone calls it gives a busy signal. They are all Radio Shack units, as I can find no other manufacturer who makes one in that voltage range.

About the same time I got the lightning strike, I converted my solar system to 24 VDC, it was a 12 VDC system up until then.  For my answering machine, DSL modem and laptop I use a Samlex SDC12 24 to 12 VDC converter.  The output reading is 13.5 VDC. Is something wrong with the Samlex causing them to fail?

I have a landline here so I called the phone company repairman and he came out here and said it was a bad answering machine.
I can't understand why 3 in a row could go bad so soon.

????

Is there an answering machine I can buy that will work directly on 12 or 24 VDC? 24 VDC would be perfect because I could bypass the Samlex.
« Last Edit: July 28, 2015, 04:29:36 PM by armadillo »

mab

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Re: 12 Volt Answering Machines
« Reply #1 on: July 28, 2015, 07:09:57 PM »
if they're designed for 9v then 13.5 might be pushing it - some may cope but not others.

rather than the samlex convertors I'd look for something like 24v-9v regulator/convertor online; depending on your electronic knowhow you could use either a simple 7809 three pin reg (up to 1 amp), or one of the complete buck converter types like this wich can be set to output anything from 1.25 - 36v and will take an input of up to 38v:-
http://www.ebay.co.uk/itm/DC-to-DC-24V-12V-9V-5V-4V-38V-to-1-25V-36V-5A-Step-Down-Power-Supply-Buck-Module-/271880445232?pt=LH_DefaultDomain_3&hash=item3f4d565d30

or something with a fixed output and self contained like:-
http://www.ebay.co.uk/itm/12V-24V-Step-Down-to-9V-5A-DC-DC-Buck-Converter-Regulator-Power-Module-R1BO-/131231427864?hash=item1e8e00ad18

dnix71

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armadillo

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Re: 12 Volt Answering Machines
« Reply #3 on: July 28, 2015, 09:49:35 PM »
if they're designed for 9v then 13.5 might be pushing it - some may cope but not others.

rather than the samlex convertors I'd look for something like 24v-9v regulator/convertor online; depending on your electronic knowhow you could use either a simple 7809 three pin reg (up to 1 amp), or one of the complete buck converter types like this wich can be set to output anything from 1.25 - 36v and will take an input of up to 38v:-
http://www.ebay.co.uk/itm/DC-to-DC-24V-12V-9V-5V-4V-38V-to-1-25V-36V-5A-Step-Down-Power-Supply-Buck-Module-/271880445232?pt=LH_DefaultDomain_3&hash=item3f4d565d30

or something with a fixed output and self contained like:-
http://www.ebay.co.uk/itm/12V-24V-Step-Down-to-9V-5A-DC-DC-Buck-Converter-Regulator-Power-Module-R1BO-/131231427864?hash=item1e8e00ad18
Thanks for your reply.
Those links are for UK ebay so I looked for step downs on US ebay. Do you think something like this would do it?
http://www.ebay.com/itm/DC-DC-15W-Converter-12V-Step-down-to-9V-3A-Power-Supply-Module-Auto-Recovery-/160986102887?pt=LH_DefaultDomain_0&hash=item257b84fc67
I'm not an electronics guy. I would connect it to the 12 VDC output of my Samlex.

armadillo

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Re: 12 Volt Answering Machines
« Reply #4 on: July 28, 2015, 09:52:09 PM »
http://www.ebay.com/itm/Panasonic-KX-TS620B-Corded-Telephone-with-Digital-Answering-Machine/111630382767

Line powered with answering machine.
Thanks Dnix.
Do you have one of these phones? I tried to look up info on that model and could not get confirmation on the power supply. A review on Amazon mentioned that it did require AC power. There is one for $36 free shipping right now.

http://www.ebay.com/itm/Panasonic-KX-TS620B-Integrated-Corded-Telephone-System-with-Digital-Answering-/252040634324?hash=item3aaecadfd4

dnix71

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Re: 12 Volt Answering Machines
« Reply #5 on: July 28, 2015, 11:51:04 PM »
The ac adapter is 6.5v. There was an eBay listing for a used one. I thought the phone didn't require an ac adapter.

ATT has a page of phones that are supposed to not require an ac adapter, but only the first two on that page actually don't have a wall adapter, and neither has an answering machine built in. http://telephones.att.com/telephones/corded-telephones/no-ac-power

Phones that will still make and recieve calls without external power are available, but the other functions won't work when the power goes out.

http://www.ebay.com/itm/Clarity-Digital-Easy-Recall-Large-Button-Answering-Machine-Radio-Shack-/201380933153 This one requires 15v.
That would be a better choice if running from a 13.5v adapter.

armadillo

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Re: 12 Volt Answering Machines
« Reply #6 on: July 29, 2015, 12:24:06 AM »


http://www.ebay.com/itm/Clarity-Digital-Easy-Recall-Large-Button-Answering-Machine-Radio-Shack-/201380933153 This one requires 15v.
That would be a better choice if running from a 13.5v adapter.
Thanks. That might be worth the gamble. 1 1/2 volts low shouldn't make any difference I don't think.

mab

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Re: 12 Volt Answering Machines
« Reply #7 on: July 29, 2015, 07:45:01 AM »
if they're designed for 9v then 13.5 might be pushing it - some may cope but not others.

rather than the samlex convertors I'd look for something like 24v-9v regulator/convertor online; depending on your electronic knowhow you could use either a simple 7809 three pin reg (up to 1 amp), or one of the complete buck converter types like this wich can be set to output anything from 1.25 - 36v and will take an input of up to 38v:-
http://www.ebay.co.uk/itm/DC-to-DC-24V-12V-9V-5V-4V-38V-to-1-25V-36V-5A-Step-Down-Power-Supply-Buck-Module-/271880445232?pt=LH_DefaultDomain_3&hash=item3f4d565d30

or something with a fixed output and self contained like:-
http://www.ebay.co.uk/itm/12V-24V-Step-Down-to-9V-5A-DC-DC-Buck-Converter-Regulator-Power-Module-R1BO-/131231427864?hash=item1e8e00ad18
Thanks for your reply.
Those links are for UK ebay so I looked for step downs on US ebay. Do you think something like this would do it?
http://www.ebay.com/itm/DC-DC-15W-Converter-12V-Step-down-to-9V-3A-Power-Supply-Module-Auto-Recovery-/160986102887?pt=LH_DefaultDomain_0&hash=item257b84fc67
I'm not an electronics guy. I would connect it to the 12 VDC output of my Samlex.

Yes that should work fine if supplied from your 12v samlex, although I was thinking it's more efficient to go direct from the original battery to 9v, rather than 24 -> 12-> 9, which is why I was suggesting units that could take >30v input.

armadillo

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Re: 12 Volt Answering Machines
« Reply #8 on: July 29, 2015, 01:02:47 PM »

Yes that should work fine if supplied from your 12v samlex, although I was thinking it's more efficient to go direct from the original battery to 9v, rather than 24 -> 12-> 9, which is why I was suggesting units that could take >30v input.
That makes sense, I just couldn't find one that converted to 9 volts unless I went with an adjustable one like this:
http://www.ebay.com/itm/LM2596-Step-down-Power-Module-DC-4-0-40-to-1-3-37V-With-Voltage-Display-Mini-New-/231314364113?pt=LH_DefaultDomain_0&hash=item35db6916d1

or this:
http://www.ebay.com/itm/DROK-DC-DC-Buck-Converter-8A-80W-Step-Down-Voltage-Converter-Power-Transformer-/252033687497?pt=LH_DefaultDomain_0&hash=item3aae60dfc9

mab

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Re: 12 Volt Answering Machines
« Reply #9 on: July 29, 2015, 02:56:34 PM »
true - if you want one pre-set for 9v then your choice is more limited; but either of those you linked would work, as long as you have a voltmeter and set the output to 9v to start with.

armadillo

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Re: 12 Volt Answering Machines
« Reply #10 on: July 29, 2015, 04:49:20 PM »
Thanks for the info, Mab. I went ahead and ordered one. Also ordered a Clarity 15 volt answering machine so I'm covered both ways.

Lark

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Re: 12 Volt Answering Machines
« Reply #11 on: September 26, 2015, 04:22:17 PM »


http://www.ebay.com/itm/Clarity-Digital-Easy-Recall-Large-Button-Answering-Machine-Radio-Shack-/201380933153 This one requires 15v.
That would be a better choice if running from a 13.5v adapter.
Thanks. That might be worth the gamble. 1 1/2 volts low shouldn't make any difference I don't think.

After reading this I bought an Easy recall machine  so could run off nominal 12 volt system and was surprised to find am doesn't work directly off battery even though most of day in 13.5 to 15 volt range. Symptom is it comes on but phones have no dial tone. If use the factory supplied ac adaptor thru Pure sine inverter part of my system phones do work!

I am used to running dc appliances directly off battery in order to save inverter and have never found a diff of few dc volts to be a problem.

So discover that ac adaptor is actually putting out steady 19 volts, tho it says 15 on it and on back of am also.

So buy powerstream upconverter with input 12-14 volt and output cchoices of 15, 18, 21,24 volts. same symptom no dial tone at any of these outputs! You'd really think at least 18v would work. hard to believe machine could be so picky.

Maybe this story helps someone and would appreciate it if anyone could  solve this. Like I guess if one could measure how much current machine draws they'd be able to use E=ir to figure out how much resistance to add to wire to drop volts from 21 or 24 to 19 exactly but frankly 2 decades rusty on all that.

dnix71

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Re: 12 Volt Answering Machines
« Reply #12 on: September 27, 2015, 12:44:18 AM »
If you have an ac adapter with the device, there is probably a full-wave bridge inside the device. I ran a Westell modem from batteries and it was happy to do so. The adapter was 13.5vac and went to a bridge inside the box. That device would run on the current provided by one half of the bridge. AC would feed both halves of the bridge, dc will only feed one half. It didn't matter in my case.

Your answering machines may need more current than can be supplied by one half of the bridge. In that case you need to open the machine and bypass the bridge. It is also possible that the bridge is used as a voltage doubler to supply higher voltage to some component. Look at the circuit first to see.

mab

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Re: 12 Volt Answering Machines
« Reply #13 on: September 27, 2015, 06:20:13 PM »
I'd be surprised if it was that picky. My guess is that the problem is to do with your dc-dc convertor not being isolated from the battery, and the battery is perhaps ground referenced? - meaning your AM is then ground-referenced too which may put your AM at a voltage relative to ground that's too different from that of the phone line, preventing the signal getting through.

When you use the ac adaptor - which probably has an isolated; i.e. floating output it allows the AM to operate at whatever voltage the phone line is at.

I guess you could try using an isolated 12v battery (with and without the upconvertor) and if that works, then that's the problem - you need an isolating dc-dc converter.

Lark

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Re: 12 Volt Answering Machines
« Reply #14 on: October 01, 2015, 03:58:51 PM »
I'd be surprised if it was that picky. My guess is that the problem is to do with your dc-dc convertor not being isolated from the battery, and the battery is perhaps ground referenced? - meaning your AM is then ground-referenced too which may put your AM at a voltage relative to ground that's too different from that of the phone line, preventing the signal getting through.

When you use the ac adaptor - which probably has an isolated; i.e. floating output it allows the AM to operate at whatever voltage the phone line is at.

I guess you could try using an isolated 12v battery (with and without the upconvertor) and if that works, then that's the problem - you need an isolating dc-dc converter.

Bingo! Thanks so much mab for the tip. Phones and answering machine do work when hooked to separate battery. However is a mystery because my 12 volt house battery is not grounded. Only run equipment grounds. 

Trouble is here that isolated dc converters are very expensive far as I can tell and designed for lot higher amp output then I need of course. Thing is I may not even need up converter as betting am would run fine off 12-13 volts dc with direct house battery connect if could isolate such.

In the past they made am's that ran on 9 volt dc so just used the cheap down converter but now they are all AC. Current machine is 9 vac and maybe is easy way to change that if open machine but obviously I'm not electronics savvy.

Anyway, any ideas on an inexpensive isolated converter or if is possible to just wire something right into line without a converter or even why this could happening if battery is ungrounded?

Lark

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Re: 12 Volt Answering Machines
« Reply #15 on: October 01, 2015, 04:04:07 PM »
If you have an ac adapter with the device, there is probably a full-wave bridge inside the device. I ran a Westell modem from batteries and it was happy to do so. The adapter was 13.5vac and went to a bridge inside the box. That device would run on the current provided by one half of the bridge. AC would feed both halves of the bridge, dc will only feed one half. It didn't matter in my case.

Your answering machines may need more current than can be supplied by one half of the bridge. In that case you need to open the machine and bypass the bridge. It is also possible that the bridge is used as a voltage doubler to supply higher voltage to some component. Look at the circuit first to see.

Thanks dnix,-was considering whether to open this machine up (which would probably break it) to see what this bridge looks like when mab answered.

mab

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Re: 12 Volt Answering Machines
« Reply #16 on: October 03, 2015, 06:18:09 PM »
Quote
Anyway, any ideas on an inexpensive isolated converter or if is possible to just wire something right into line without a converter or even why this could happening if battery is ungrounded?

hmm, sorry there are probably no cheap isolating dc dc convertors - certainly not that I'm aware of.

as to your battery grounding; well if you have lots of things connected it's not a surprise that something's grounding it; the inverter would be my first guess if it's wired into the house electrics, but not necessarily. Even having cables going out to solar panels and lying on damp ground can develop enough leakage over time - maybe.

Lark

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Re: 12 Volt Answering Machines
« Reply #17 on: October 03, 2015, 07:06:20 PM »
Yeh, I'm not totally cheap so will have to look some more but memory is were in the several hundred dollar range. Plus, think they went right to output of 24vdc, nothing in between like 15 or 18vdc.

Rechecked inverter. Nothing. Will have to try and track down any possible leaks to ground somewhere I guess   :(

Guess there's nothing can just wire right into line to act as isolator. Don't think I need a dc converter

Remember being convinced by an old homepower mag article long ago that avoiding electrical ground and just doing equipment ground would protect against lightening. House has taken 2 direct hits in past and all I lost was the internet router/modem.  :)

bart

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Re: 12 Volt Answering Machines
« Reply #18 on: October 04, 2015, 07:37:22 AM »
   Don.t know if this is exactly what your looking for, but does accept wide range of input / output voltages. I have one that is being used on a headway battery pack and it works well.

http://www.amazon.com/gp/product/B00C5W2BPS?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00

Lark

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Re: 12 Volt Answering Machines
« Reply #19 on: October 06, 2015, 11:26:11 PM »
Thanks Bart but doesn't look like that one is isolated. Does anyone know what kind of components are used in an isolated converter that give it this feature? Strange that this feature makes it so expensive by at least a magnitude Best I found that puts out less then 24 vdc is a Lind electronics unit 12-20v that is $250.00

Lark

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Re: 12 Volt Answering Machines
« Reply #20 on: October 06, 2015, 11:35:13 PM »
Barring all that it would just be so super if someone could advise on any faster way to track down battery leaks to ground.

Wish i'd bought a few extra of those older answering machines like I had that had a 120vac to 9vdc adapters and ran fine on simple down converter or actually even without. wearing out an expensive outback just to keep am on is not acceptable  :(

DamonHD

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Re: 12 Volt Answering Machines
« Reply #21 on: October 07, 2015, 03:06:07 AM »
A silly question for you, but is your phone company able to provide a (free) answering service at the exchange?

Ours does and so we haven't run an answering machine at our house for many years.

Would get round the problem!

Rgds

Damon
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OperaHouse

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Re: 12 Volt Answering Machines
« Reply #22 on: October 07, 2015, 07:48:30 AM »
Fairly simple problem but it can involve a LOT of searching.  9V is not that common in industry and military units would be speced at 28V input.  I figure you need 3W and that could be made up from two 5V units in series, a diode or two could provide the voltage drop to 9V if necessary.  Here is a fairly deluxe quality unit.
  http://www.ebay.com/itm/PT4105C-15-WATT-24V-TO-5V-12V-15V-ISOLATED-DC-DC-CONVERTER-/271880981718?hash=item3f4d5e8cd6

Output is actually 12V for this one and that could be reduced further with a 2596 switcher module for less than $2.  You really should identify your country in the profile for tailored solutions.  It doesn't have to be expensive, just takes an understanding of what to search for and a lot of searching.  The solution could easily be less than $6.


Lark

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Re: 12 Volt Answering Machines
« Reply #23 on: October 08, 2015, 12:19:53 AM »
Hey, this is great OperaHouse! had tried going thru a few ebay pages before but didn't find this. confused about your reference to 9 volts though. What trying to do is run the above "easy recall" answering machine (only cause only am I know of will run on dc), which requires 15-19vdc off a house 12 volt battery that apparently has some hidden ground somewhere so need converter to be isolated.

it appears the output of this unit can be varied between 5,12 and 15vdc so I can choose the 15v. Only problem is input is 24vdc so will need to string in the cheap powerstream upconverter I mentioned above to create 24 from 12. then input this 24 into the Pt4105c. Kind of clunky but lot better then nothing.

Answer machine can run on anything up to 19vdc as that's actually what ac adaptor puts out so of course the ideal would be an isolating upconverter with 12vdc input but not finding yet. will try this while keep looking for where my battery is being grounded. been trying a little but it appears to be a real stumper. maybe is an underground wire but geez, used Uf wire or put in pvc

Thank you

OperaHouse

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Re: 12 Volt Answering Machines
« Reply #24 on: October 08, 2015, 09:31:17 AM »
The thread got convoluted.  First poster wanted 9V for an answering machine and he had upgraded to 24V battery.  That 4105C is 12V and not adjustable, if 4105C is what they are selling. This is a lister that pulls pictures from a catalog.  There are numerous listings for 4 or 5 cheap converters for a couple of bucks.  They can be placed in series or parallel to get voltage or current you want.  The following is an interesting video that shows these little modules are quite capable.

http://www.eevblog.com/2012/07/31/eevblog-324-dc-dc-converter-testing-usb-supply-part-4/

OperaHouse

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Re: 12 Volt Answering Machines
« Reply #25 on: October 08, 2015, 10:39:50 AM »
Two or three of these isolated 1W modules in parallel ought to work also.  These would be a nice supply for simple high side FET drivers.
http://www.ebay.com/itm/Isolated-Power-Module-w-4pins-DC-DC-Converter-In-10-16V-Out-12V-1W-/360860072660?hash=item5404efbad4