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Subaru
1-3-2-4
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join:2001-05-31
Greenwich, CT
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1 edit

battery backup lights

I thought about doing this a few years ago but now I'm getting a bit more serious about it, one thing I can't remember is how do you get the lights (in this case LED's) to stay off until the power fails? I was thinking 350 mA should be enough for the hallway and dining room area. At the time being I was thinking about using a 17 Ah battery with a 350 mA driver powering 3 LED's in series.

I have two of these here:
»www.ledsupply.com/creexre-rb.php

and a single 3-Up neutral white which the LED's still work but something fell on the dies while curing on a heatsink.

»www.ledsupply.com/07007-pw740-l.php


SparkChaser
Premium
join:2000-06-06
Downingtown, PA
kudos:4
anything from a simple relay to a opto coupler would provide an isolated signal that the power is on. When that signal changes state you've lost power.



Subaru
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join:2001-05-31
Greenwich, CT
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I'm sure a relay would be a bit more simple, I can't figure out how long of a runtime I would get.. I would guess around maybe 19-22 hours?

lutful
... of ideas
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join:2005-06-16
Ottawa, ON
kudos:1
said by Subaru:

can't figure out how long of a runtime I would get.. I would guess around maybe 19-22 hours?

Typical 3 LED setup will be consuming about 350mAh each hour.

With a new fully charged 17Ah battery, maximum run time would be about 40 hours but you should really implement a cut off to prevent battery voltage from dropping below 10V.



Subaru
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Greenwich, CT
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Heh I was off a bit on that :P Not too sure if I would be 40 hours without power.. the hurricane sandy was different.. normal storm stuff it's maybe 5 hours at best..

So for an AC relay I would be looking for a N/O relay?


shdesigns
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Stone Mountain, GA
An normally closed relay on the power connected to an AC source. When power is lost, it closes and turns on the power to the LED's.


Subaru
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Greenwich, CT
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So something like this would be ok?

»www.mouser.com/ProductDetail/Omr···nUCcPAza

10A should be more then enough rated

and I was thinking about building this charger.. i'd just need the IC and jack and that's about it.. I have the rest here.

»www.instructables.com/id/DIY-Lea···Charger/
--
It's NOT Ni-kon It's NE-KON!




LG is NOT Lifes Good It's Lucky Goldstar!



SparkChaser
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Downingtown, PA
kudos:4
reply to Subaru
Yes, that relay would work. You use the NC contacts as shdesigns See Profile said.


Subaru
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join:2001-05-31
Greenwich, CT
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said by SparkChaser:

Yes, that relay would work. You use the NC contacts as shdesigns See Profile said.

I was looking in the data sheet something like this..

SPST-NO Semi-sealed G2R-1A

SPDT Semi-sealed G2R-1

I would assume that G2R-1 would be NC since it does not list anything right?
--
It's NOT Ni-kon It's NE-KON!




LG is NOT Lifes Good It's Lucky Goldstar!



SparkChaser
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join:2000-06-06
Downingtown, PA
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A SPST would not have a normally closed contact. It has to be SPDT.


Subaru
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Greenwich, CT
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said by SparkChaser:

A SPST would not have a normally closed contact. It has to be SPDT.

got it, now I just need to find a driver that I have left over.. not sure if royal blue would be great for the hallway since the wavelenth is 450nm.. I had them in the kitchen for awhile and everything florescent was glowing


Sc0tt
Kneedragger
Premium
join:2000-11-13
Stockholm, NJ
reply to Subaru
if you want an easy out, they're only about $20 online.

for that cheap, it may be fun just to grab one and modify it to your liking.


Subaru
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Cheap way out too easy only a few things I need to order, I would be using a small aluminum bar as a heatsink.


Subaru
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Greenwich, CT
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reply to Subaru
ah poo can't find the 1 amp driver, I can at least I can start with the sla charger.

I saw two.. one being a bit more in-depth.. and the other one is simple.

Having said that the simple one does not seem to trickle charge? I haven't messed too much with SLA but I know the charge rates are low but is it safe to keep a charge on it long term?

Complex charger circuit
»www.talkingelectronics.com/proje···SLA.html

simple

»www.instructables.com/id/DIY-Lea···r/#intro
--
It's NOT Ni-kon It's NE-KON!




LG is NOT Lifes Good It's Lucky Goldstar!



shdesigns
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1 recommendation

I have one I used:

»shdesigns.org/gcellchg.html

I set it to 13.4V. Will charge fast for the the first 75% then ramps down to 0.

It is what is called a "float charger".
--
Scott Henion

Embedded Systems Consultant,
SHDesigns home - DIY Welder


Subaru
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Greenwich, CT
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That design looks good and the LED is a nice touch so after I get my battery (might use one I have already) I just find what the charge settings are and just set it to that?


shdesigns
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Yes, see what the OEM says for float charge voltage.


Subaru
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Greenwich, CT
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I will have a check, I hope it's listed on the battery, btw nice use of off the shelf parts, I have everything listed but the heatsink and the N22222A

My project box may be a little small but I have at least 3 sizes laying around


shdesigns
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Nearly any general purpose NPN transistor will do.

Will need a heat sink. I used a box about the size of a biz card and 1" tall. I replaced the cover with an aluminum plate that doubled as a heat sink.

Works best with about 16V in, higher is just wasted as heat. I use it with a solar panel to keep my riding mower batt charged.
--
Scott Henion

Embedded Systems Consultant,
SHDesigns home - DIY Welder


Subaru
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Greenwich, CT
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did you take any measurements of the heatsink? I don't know if I have any spare transformers but say it had a 15-17 Vout voltage.. trying to get an idea if that's too hot to run in a case without a aluminum plate but with a heatsink on it..

if it's really bad I could add a small 40 mm fan to the case


SmokChsr
Who let the magic smoke out?
Premium
join:2006-03-17
Saint Augustine, FL
reply to shdesigns
said by shdesigns:

I set it to 13.4V. Will charge fast for the the first 75% then ramps down to 0.

Nice little design, The one thing I think I would add is an isolation diode so that the charging circuit didn't become an additional load upon failure. (especially if you need the 1K for the LM317) Of course you would have to compensate for the diode drop with the regulation setting.


shdesigns
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The design was parts I had laying around.

Id probably do a switching reg if i was doing one from scratch.


Subaru
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1 edit
reply to Subaru
Click for full size
Click for full size
is it possible to use another trim pot since to get a 4.7 k ohm I would have to order in bulk.

the only trim pot I have here is I think it's 10 k ohm all it says on it is 104-W I'm trying to check with my meter but hard without clip leads but it seems to have a wide range with a short turn so it must be single turn..

Oh never mind it's 100k


Subaru
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1 edit
reply to Subaru
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Going to use this battery it's from my jump pack unit still good at rest it's at 12.6v

model number behind foam is 6-FM-17


Subaru
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reply to Subaru
Click for full size
So this is where I stand now, the relay is not soldered down just yet, I went to the wrong radio shack that closed early so I was unable to pick up the DC jack and plug and #6 ring terminals.

I was wondering about voltage and not wanting to fall under 11.6 V since this project box is pretty big I was thinking about putting a analog voltage meter in it, but wondering if it was possible for it to switch off once it hits the 11.6V threshold?
--
It's NOT Ni-kon It's NE-KON!




LG is NOT Lifes Good It's Lucky Goldstar!


lutful
... of ideas
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join:2005-06-16
Ottawa, ON
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1 recommendation

said by Subaru:

... thinking about putting a analog voltage meter in it, but wondering if it was possible for it to switch off once it hits the 11.6V threshold?

If you want something more fun, build a 12V battery monitor with red/yellow/green leds to show exact charge status. You can skip D1 (first red LED) and use that pin to drive the relay which turn off power to your white LED driver.

»www.electronicecircuits.com/elec···-circuit

Less fun way requires a comparator with built-in voltage reference to control the relay. You use a voltage divider to match the battery cut-off voltage to the reference voltage.


Subaru
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join:2001-05-31
Greenwich, CT
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1 edit
said by lutful:

said by Subaru:

... thinking about putting a analog voltage meter in it, but wondering if it was possible for it to switch off once it hits the 11.6V threshold?

If you want something more fun, build a 12V battery monitor with red/yellow/green leds to show exact charge status. You can skip D1 (first red LED) and use that pin to drive the relay which turn off power to your white LED driver.

»www.electronicecircuits.com/elec···-circuit

Less fun way requires a comparator with built-in voltage reference to control the relay. You use a voltage divider to match the battery cut-off voltage to the reference voltage.

You know I was thinking about this but just a simple 3 LED setup

I have two quad comparators but I don't think they have a voltage reference. The two I have are LM339N & CD40106BE wait that's a Schmitt trigger

Also I don't own a adjustable power supply just yet.
--
It's NOT Ni-kon It's NE-KON!




LG is NOT Lifes Good It's Lucky Goldstar!



Subaru
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Greenwich, CT
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reply to Subaru
This looks simple enough and offers SC protection & OC protection

I assume since the variable resistor value is not listed it does not really matter?

»homemadecircuitsandschematics.bl···oad.html

but I would still need to order the transistors it seems

lutful
... of ideas
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join:2005-06-16
Ottawa, ON
kudos:1
said by Subaru:

This looks simple enough ...
»homemadecircuitsandschematics.bl···oad.html

I notice the same person (Swagatam Majumder) posted a complete LED backup lamp circuit this month:
»homemadecircuitsandschematics.bl···000.html

It is almost exactly what you are trying to do.


Subaru
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Greenwich, CT
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1 edit
yeah I saw that when I did a search but since I pretty much built the charging circuit going to leave as is but just add in the low voltage cut off.

I see he used a op amp in that one but not the first one..

Maybe I can use the LM741 instead of his first design.. one thing is can't get that transistor local nor do I have that zener.