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small, adjustable time delay 12v relay.


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_oswald 
Member - Posts: 7
Member spacespace
Joined: January 26, 2009
Location: Minnesota, United States
Posted: January 27, 2009 at 9:36 PM / IP Logged  
Good evening, all.
I'm about ankle-deep in a hobby project that requires four different 12v heating elements to be turned on, held on, turned off - with this cycle being repeated as long as voltage is applied. Currently, I'm thinking that four independent adjustable time-delay 12 volt relays would work for the task.
However, I don't have much experience with relays and I'd appreciate any suggestions or discussion on the matter before I make any purchases. I'm also open to using another method to achieve the same goal - if there was a project kit to achieve a similar end I'd be interested in McGuyvering it to fit.
Thanks,
Erik
KPierson 
Platinum - Posts: 3,537
Platinum spaceThis member consistently provides reliable informationspace
Joined: April 14, 2005
Location: Ohio, United States
Posted: January 27, 2009 at 11:01 PM / IP Logged  

Can you supply more information on what exactly you are trying to do.

Also, what kind of timing will be involved in the heaters?  Will they all be on or off at the same time, or will they be staggered with overlap.  It's really hard to advise on a system without having all the information.

Kevin Pierson
_oswald 
Member - Posts: 7
Member spacespace
Joined: January 26, 2009
Location: Minnesota, United States
Posted: January 27, 2009 at 11:10 PM / IP Logged  
KPierson wrote:

Can you supply more information on what exactly you are trying to do.

Absolutely.
One of my hobbies is making costumes of heroes or villains. With 'The Watchmen' coming out on March 6th, I'm working on a totally awesome costume based on the character Rorsarch. Using a color changing fabric responsive to temperature, I intend to have heating elements placed under a mask made of the aforementioned fabric that turn on/off at different times - creating an ever-changing pattern.
KPierson wrote:

Also, what kind of timing will be involved in the heaters?  Will they all be on or off at the same time, or will they be staggered with overlap.  It's really hard to advise on a system without having all the information.

I'll explain how the heating elements are laid out, and then explain the timing. The mask will have four 'zones'. For instance, 'Zone 1' would be heating elements placed on the cheeks, 'Zone 2' would be elements placed over the nose and so-forth.
Each zone would turn on and off independently. That way the mask doesn't present the same pattern all of the time. Ideally each zone would also have a different amount of 'hold', to better attempt to make it appear more random.
I apologize if my original post lacked information. I really didn't know how to approach this request without seeming overwhelmingly strange. :)
Thanks,
Erik
hotwaterwizard 
Silver - Posts: 1,350
Silver spacespace
Joined: December 11, 2003
Location: California, United States
Posted: January 28, 2009 at 12:54 AM / IP Logged  

Ok we need more Info

All on at the same time?

One at a time in Sequence?

How much time between cycles etc. Explain better please.

Help us to help you???

John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !
_oswald 
Member - Posts: 7
Member spacespace
Joined: January 26, 2009
Location: Minnesota, United States
Posted: January 28, 2009 at 3:10 AM / IP Logged  
hotwaterwizard wrote:

Ok we need more Info

All on at the same time?

One at a time in Sequence?

How much time between cycles etc. Explain better please.

Help us to help you???

All four of the circuits would receive power at the same time, but because they'd be time delayed, the heating elements would not all turn on at the same time.
They'd be one-at-a-time, with each heating element drawing from it's own circuit to the battery.
The time between cycles would be different for each circuit, but I'd say that a 'safe' guesstimate would be variable up to (maybe) six or eight seconds.
hotwaterwizard wrote:

I adapted this Circuit for Relays.

posted_image

Thanks. From what I gather off the original site, changing the C1 value changes the 'sequencer speed'... do you suppose that is the time for 'on' or for the length of time the relay is held 'on'? Ideally, they'd be independent values.
KPierson 
Platinum - Posts: 3,537
Platinum spaceThis member consistently provides reliable informationspace
Joined: April 14, 2005
Location: Ohio, United States
Posted: January 28, 2009 at 10:52 AM / IP Logged  

How big are the heaters (voltage and wattage rating) that are going to be used?  That would dictate how exactly I would go about doing it - I would try to stay away from relays personally as they will just be an additional load on the battery.

The "issue" with a simple time delay circuit is that you won't have any randomness to the pattern.  You would need a much more intelligent controller to provide a 5-6 minute on/off pattern - this would give the illusion of randomness as most people wouldn't notice patterns repeating after that amount of time.

What kind of space do you have to work with? 

Kevin Pierson
_oswald 
Member - Posts: 7
Member spacespace
Joined: January 26, 2009
Location: Minnesota, United States
Posted: January 28, 2009 at 1:31 PM / IP Logged  
KPierson wrote:

How big are the heaters (voltage and wattage rating) that are going to be used?  That would dictate how exactly I would go about doing it - I would try to stay away from relays personally as they will just be an additional load on the battery.

The "issue" with a simple time delay circuit is that you won't have any randomness to the pattern.  You would need a much more intelligent controller to provide a 5-6 minute on/off pattern - this would give the illusion of randomness as most people wouldn't notice patterns repeating after that amount of time.

What kind of space do you have to work with? 

Truthfully, I don't know what kind of voltage/wattage I'm working with. I found some flexible heating elements by Minco at a local surplus store ( Minco / Polimide Heaters) lacking in just about any information. When we started putzing around with them on a Variac, we came to believe they are designed for 12v, 1A.
Whatever company contracted them in the custom design that ended up there is wonderful for this project, though. I can take a picture when I'm at home tomorrow. Funky stuff.
And I'm all for moving away from relays, if I can find a better option. I was hoping that maybe there was an IC project out there just -perfect- for this, because it would be less draw and occupy less space.
Oh, and on space - I'm looking to mount this on something similar to a shoulder brace, with wires running up into the mask to the heating elements.
posted_image
It'd be worn under a shirt and under a jacket, so it'd be neatly concealed.
KPierson 
Platinum - Posts: 3,537
Platinum spaceThis member consistently provides reliable informationspace
Joined: April 14, 2005
Location: Ohio, United States
Posted: January 28, 2009 at 2:39 PM / IP Logged  

What kind of battery are you going to use?

With a 1A heater I would recomend a 3A low on-resitance mosfet driver for each heater.  The low on-resistance will minimize the heat dissipation of the mosfet.

Kevin Pierson
_oswald 
Member - Posts: 7
Member spacespace
Joined: January 26, 2009
Location: Minnesota, United States
Posted: January 28, 2009 at 10:33 PM / IP Logged  
KPierson wrote:

What kind of battery are you going to use?

With a 1A heater I would recomend a 3A low on-resitance mosfet driver for each heater.  The low on-resistance will minimize the heat dissipation of the mosfet.

As of current, I'm looking into using a Makita tool battery pack. I'm not sure on the voltage, because I don't have them on hand - a friend of mine is working on checking a few he borrowed from the 'bad' bin and restoring as necessary.
wiringfool 
Member - Posts: 21
Member spacespace
Joined: October 22, 2006
Location: United States
Posted: February 11, 2009 at 9:16 PM / IP Logged  
here a simple idea would gun lock timers that are used for approx 15 sec time on work the amp capacity should be fine and might be easier to work in that config
wiringfool eieioztztzt
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