It is currently Tue Jan 16, 2018 7:18 am

All times are UTC - 8 hours




 Page 1 of 1 [ 7 posts ] 
Author Message
 Post subject: Blinking red LED with a coin [button] cell
PostPosted: Sat Oct 14, 2017 5:31 am 
User avatar

Joined: Sat Feb 12, 2005 1:01 am
Posts: 79
Location: On the bank of, and sometimes in the Castor river
Using an "off the shelf" red blinking 5mm LED [3v. 20 ma] and a small current limiting resistor controlled by a tilt switch (very simple so far) but since small size is very important I would like to power this with a coin cell [button cell] or two that are no larger than a quarter [25 cents] and no thicker than 1/4". This will be encased in epoxy so changing the battery is not an option.
The desired end result would operate [on blinking] for 10 to 15 seconds around 4 or 5 times in a 24 hour period and last as long as possible. A year would be perfect.
Coin cells like a CR2477 have a 1000 mAh rating which to a novice like me means that it would operate a 20 ma LED for a long time. I want to make a "PUT THE TOILET SEAT BACK DOWN" reminder to "attempt" to teach my son and keep both of us out of trouble. Seat up - light blinks and seat down it's off.

Am I on the right or wrong track with the battery choice? Does anyone have a better battery choice?

I am open to any and all suggestions and thanks in advance for reading this.



_________________
cNd
Offline
 Profile Send private message  
 
 Post subject: Re: Blinking red LED with a coin [button] cell
PostPosted: Sat Oct 14, 2017 7:57 am 

Joined: Fri Aug 22, 2003 12:01 am
Posts: 1612
Location: (somewhere), Afghanistan; from Rochester, NY
CR2477s are only 3V when brand new and under no load. They are considered "dead" when voltage is down to 2V.

The blinking LEDs I found are 3.5V minimum to 14V maximum. Your circuit with one CR2477 might last a week, if it worked at all.

I suggest two CR2477s in series. That would be 6V new, 4V dead. Recalculate the resistor. Since 4V is greater than 3.5V, and short period at 20mA is a vveerryy light load, it could last a couple years.

Cheers,



_________________
Dale Y
Offline
 Profile Send private message  
 
 Post subject: Re: Blinking red LED with a coin [button] cell
PostPosted: Sat Oct 14, 2017 10:11 am 
User avatar

Joined: Sat Feb 12, 2005 1:01 am
Posts: 79
Location: On the bank of, and sometimes in the Castor river
Thank you for your reply. As I mentioned in my original post - there is room for two (stacked) no more than 1/4" high total. I will solder them.
Thanks again.



_________________
cNd
Offline
 Profile Send private message  
 
 Post subject: Re: Blinking red LED with a coin [button] cell
PostPosted: Sat Oct 14, 2017 12:55 pm 

Joined: Fri Aug 22, 2003 12:01 am
Posts: 1612
Location: (somewhere), Afghanistan; from Rochester, NY
To meet thickness limit put the two CR2477s side by side with a wire (or flat metal strip) from bottom of one to the top of the other.

Or stack two CR2330s. They are a touch less than 1/8 inch thick each. How you would solder them together I don't know, because solder does not "wet" the metal batteries are made of. Even top and bottom wires will be a problem. Maybe heat shrink tubing to squeeze together.

Or, Or look for coin cell holders that are 1/4 inch, or less, tall and put side by side. (for either cell type)

I don't see a single cell way to get the 3.5V minimum for blinker.

Cheers,



_________________
Dale Y
Offline
 Profile Send private message  
 
 Post subject: Re: Blinking red LED with a coin [button] cell
PostPosted: Sun Oct 15, 2017 12:02 pm 
User avatar

Joined: Sat Feb 12, 2005 1:01 am
Posts: 79
Location: On the bank of, and sometimes in the Castor river
Thanks again dyarker, since this is still in the "brain-fart stage" the first attempt will probably go into a Tic Tac container [cut down] and filled with epoxy Just in case it falls off. I will hold it on with a double sided sticky tape.
When I get it de-bugged I will post a picture.
Thanks again.



_________________
cNd
Offline
 Profile Send private message  
 
 Post subject: Re: Blinking red LED with a coin [button] cell
PostPosted: Mon Oct 16, 2017 9:51 am 
User avatar

Joined: Sat Aug 12, 2006 4:17 pm
Posts: 1273
Someone already made one.

http://tipalert.com/


Signed: Janitor Tzap


Offline
 Profile Send private message  
 
 Post subject: Re: Blinking red LED with a coin [button] cell
PostPosted: Mon Oct 16, 2017 11:03 am 
User avatar

Joined: Sat Feb 12, 2005 1:01 am
Posts: 79
Location: On the bank of, and sometimes in the Castor river
Yes I know - but that one(s) make sounds, don't last very long, and I just want to make it myself. :grin:



_________________
cNd
Offline
 Profile Send private message  
 
Display posts from previous:  Sort by  
 Page 1 of 1 [ 7 posts ] 

All times are UTC - 8 hours


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to: