Another problem... PIC?

[LiNx]

I've done some more research on relays, and found out that they have fairly low lifespans. Considering that my device will be switich on and off about once a second, I need to find something else.

What I want to do is when a small voltage is applied (less than 6 volts), it connects one circuit, and when voltage isn't being applied, it connects another circuit. Exactly like a SPDT relay, except it can't be a relay.

If anybody could direct me where I could learn more about PICs, or what exactly I would need to do this, that would be great.

Thanks in advance
-LiNx

 

[Oznog]

What's your load like? You could use a transistor.

 

[Nigel Goodwin]

I would suggest you tell us EXACTLY what you are doing, then we can make informed suggestions.

 

[ljcox]

As Nigel we need more info. It sounds like a simple switching issue.

Easy to do in hardware, probably no need for a PIC.

Len

 

[LiNx]

Okay.

It's the HD light on the computer - about 4-5 volts - which will be triggering the relay type thing.

When the HD light is supposed to be on, it's going to trigger one set of LED (inside the case - i've got a fancy nice little window cut out) - lets say red LED's.

When the HD light is supposed to be off, it's going to trigger a different set of LED's , lets say orange LED's.

The sets of LED's only take between 3.2 and 3.8 volts to power them - both of the voltages are extremely low.

So, the idea is, that whenever there is HD activity, two colors of lights will be flickering on and off inside the case.

- All just like a SPDT relay.

Thanks
-LiNx

 

[ljcox]

Here is a suggestion for you.

Select the resistors in series with the LEDs according to the brightness you want.

Len

 

[Roff]

Len, I think you should add a resistor (10k maybe - not critical) from Q1 drain to VCC. Otherwise, the gate of Q2 will take a long time to reach VCC.

Ron

 

[ljcox]

Len, I think you should add a resistor (10k maybe - not critical) from Q1 drain to VCC. Otherwise, the gate of Q2 will take a long time to reach VCC.

Ron

Yes, I was thinking about that myself. It depends on how much voltage is across the LED (or LEDs) when they are on. All that charge has to drain away.

So I have revised the drawing.

Len

 

[LiNx]

Okay... By the description underneath the drawing, it looks like that's exactly what I want, but I really don't understand how it works... Do you think anybody could explain exactly what's happeneing in the diagram?

Thanks
-LiNx

 

[ljcox]

When A is low, Q1 is off so its drain is at +5 Volt (LEDs1 are off), thus this voltage is applied to the gate of Q2.

This turns Q2 on and so the LEDs2 glow.

When A is high, Q1 is on (so its drain voltage is small), LEDs1 glow and the gate of Q2 is low and so it is off and LEDs2 are off.

Len

 

[LiNx]

Kinda bringing a thread back from the dead...

What part number would I need for the transistors? I want to find a site that will just send me a free sample so I don't have to pay... I can't find any site that has free 2N7000's.

 

[ljcox]

You will have to search for a similar transistor to the 2N7000. It is not critical. N channel MOSFET with adequate voltage rating and current rating for Vcc and the LED currents.

I bought some 2N7000 transistors recently for 23 cents each!

Len

 

[LiNx]

You will have to search for a similar transistor to the 2N7000. It is not critical. N channel MOSFET with adequate voltage rating and current rating for Vcc and the LED currents.

Will do.. Thanks

I bought some 2N7000 transistors recently for 23 cents each!

Len

Yeah... See, thing is... I don't have a car, and my mom bitches at me any time I ask her to take me somewhere... Can't really get to an electronics store


EDIT: What about the LM2727? - **broken link removed**

 

[JimB]

... I can't find any site that has free 2N7000's.

Jeez! what a cheapskate, deep pockets and short arms.

 

[LiNx]

... I can't find any site that has free 2N7000's.

Jeez! what a cheapskate, deep pockets and short arms.

Hehe... That did come out really bad. Wouldn't you rather get something for free rather than paying... Even if it is only 23 cents?

Wait... That came out really bad too... Maybe I'll just pay the 23 cents.

 

[JimB]

Yeah... See, thing is... I don't have a car, and my mom bitches at me any time I ask her to take me somewhere... Can't really get to an electronics store

Just tell her she will have to find a gas station that gives free samples.

 

[LiNx]

Heh! What the hell... It's worth a shot.

Thanks for all your help (even though it was a long shot from "contructive" critisism)...

 

[LiNx]

What about the LM2727? - **broken link removed**

Will that work in place of a 2N7000?

 

[ljcox]

What about the LM2727? - **broken link removed**

No not suitable. This is not an N channel MOSFET it is an IC that contains an N channel MOSFET. The VN10KM or similar would do.

Len

 

[Mike - K8LH]

2N7000's are 13 cents each at glitchbuster and shipping is a mere 1.85...

I usually buy them 100 at a time for the Lab Bench from Mouser (less than .10 each last order last year)...

Good luck... Regards, Mike