New and Need Help Identifying Certain Components

[OsirisGuy]

Hey I just came across this site today and it looks great. I am not a daily builder of electronic components and would like to learn more and become more experienced with them.

For the past few days I've been searching for parts for this idea I've been playing around with in my head. There are two pieces I'd like to use, however I do not know if I am identifying them correctly, if they do exist, although I'm almost 100% positive they exist in some form or shape. I'm going to try and describe as best as I can lol. The first I guess I can describe it as a resistor but operates in the opposite manner. Instead of lowering the voltage I would like a component to not pass any voltage until a particular voltage. For example my circuit will work on 12v DC, I would like the component to prevent a 9v from a relay and only when the wire carries 12v the component allows it pass and into the relay.

As I am thinking my design over and the purpose, it seems a lower, 9v does not seem like a bad idea after all, although I would still like to know if it exists, and what it would be called.

I thought perhaps a voltage regulator since I would like to resist spike voltages as well I guess, but then if the whole 9v idea works would the resistor negate that lower current if resistor was there for 12-14v?

In that sense you can say I am looking for some sort of "voltage gate" i.e. a gate which only allows a certain voltage through it neither higher or lower.

As for the second part I am searching for, is a heating element. A strip of metal preferably, which when voltage is sent through it heats up and warms (essentially a vehicles rear window defroster). I know the metal needs a high resistance but not which metals do. I need it to heating to be safe, both to the touch (80 degreesF) and the metal to be safe.

Thanks a lot folks for reading all that if you did lol. Just be glad I didn't write my life's story!

 

[saturn1bguy]

In that sense you can say I am looking for some sort of "voltage gate" i.e. a gate which only allows a certain voltage through it neither higher or lower.

What are you building, i.e. what's your idea?

There may be an easier/better way to get there than with unobtanium, AKA voltage gates and warm heating elements

 

[Mikebits]

What are you building, i.e. what's your idea?

There may be an easier/better way to get there than with unobtanium, AKA voltage gates and warm heating elements

Lol, unobtanium, I had to look that up.

Unobtainium is a humorous term that refers to an extremely rare, costly, or physically impossible material needed to fulfill a given design for a given application. The name is a blend derived from unobtainable + ium (the suffix for a number of elements). Variations include unobtanium and unattainium, with the same meaning.

Too funny

 

[Mikebits]

For the first part of your question. Sounds like maybe a **broken link removed** might be what you want.

Don't know squat about heating elements other than you run current through them and they get hot.

 

[saturn1bguy]

For the first part of your question. Sounds like maybe a **broken link removed** might be what you want.

(That's a nice reference page, Mike.)

OsirisGuy: Look at Mike's referenced page for "Voltage Window Detector Circuit." That will help you with selecting a particular level whilst ignoring those above and below.

As for heating elements, they get hot unless *controlled* to be warm, like the 80F you specify...

 

[OsirisGuy]

Okay not enough time to read that all right now. lol

So my first idea is for automatic headlights. I was thinking of using a photoresistor connecting to an automotive relay. When the light shines on the resistor it will allow the relay to be NC (pin 87) however I was not going to hook that pin up. When it got darker, at a certain voltage, the relay would disengage and then be NO (pin 87a) which would be connected to the headlights and light them up. I don't want the relay to disengage at very lil voltages and such. I think I should figure out what voltage the photoresistor will conduct first I guess. While I'm on the subject I was thinking of using this (.pdf) if I can get an opinion on it. Sorry I must of left out a lot of information there but it is very late here. I will try and explain better tomorrow.

The second idea was for heated mirrors.

My object is to build them from scratch, I know I can purchase kits but I am more interested in developing it myself.

 

[OsirisGuy]

I tried drawing a diagram, I do not know how correct it is per normal standards but I will try and explain it as best.

I would like to bypass the switch using a photoresistor/transistor and an automotive relay. As the sun shine it allows current to pass engaging the relay. Pin 87 on the relay is not hooked up to anything. When light hits the photo and the current stops, the relay switches between pins 30 and 87a closing the circuit and thus lighting the headlights.

Anyone know of a way to then have a controlled heating element then? Or a way for it to switch off after a certain temperature is reached?

I also had another idea, is it possible to get just a small LCD screen to display only a number or letter? If so where? How hard are LCDs? Any good information about LCD projects? And would it be possible to have it open and display "N" for neutral, then have 6 different pins, or closing circuits to display 1 through 5 and "R" for reverse?

Hey guys, I know this might all be a wild goose chase but I appreciate all your help. I look forward to learning so much here.