Quick Transistor Question

[skeeterb]

I want to use transistors in my control circuit, but am at a loss as what connects where. I need in my circuit diagram transistors to act as switches. How would I connect them if I wanted them to switch when one section of my main circuit loses power, turning on or Off LEDs. The way I want it, the transistors will switch when there is a loss of current going between the two posts of the upper or lower water level sensors, thus activating each individual LED or series of LEDSThis is kind of an offshoot of the thread Control Circuit help. I have established the main portion of the circuit and now I want to be able to control the indicator circuit that I have also designed, with the aid of my fellow members here on this forum. . I've been redesigning the circuits using PCB Artist and have compacted the circuits to a much smaller area. I just can't figure out how to output them in an image format that can be posted here.

 

[shaneshane1]

you could use a PNP transistor, the (E) Emitter could go in series with your LED's/resistor to +V and the (C) Collector would go straight to 0V and the (B) Base would be your switch to allow the LED's to light when the power goes low, you could use a pulldown resistor on the Base, eg: 20K from Base to 0V

Make sure your input (+V) to base has slightly less resistance than the 20K pulldown, eg: 10K to base from device that you are using, so when your device turns off, the 20K resistor will act as the negative (off) that you want for your LED's to come on!

You can go here to look at more on transistors

 

[skeeterb]

I already know of that site, that is where I started getting some of my information about the 4011 and 4093 Logic ICs. I found something in a link to another page on the site that has a transistor used an inverter (NOT Gate). I put that in the circuit, now I need some method of testing the circuit with signals passing between the upper and lower water level sensors, and the output signal of the circuit. This thread was created so I could link my control circuit with my indicator circuit, and turn on and off LEDs that indicate circuit status.

 

[ikalogic]

skeeterb, I want to share with you my transistor tutorial:
**broken link removed**
I think it can help you to summarize basic transistor knowledge.
Hope this can help.

 

[skeeterb]

Thanks man. I need all the help I can get. I'm wanting to get this circuit working as soon as possible. I'm doing research on the etching of my own PCBs now, so that I can make my own circuit boards to my specifications.

 

[BaCaRdi]

Very Impressive Tut

Thanks for that, I will add it to my collection.

-BaC

skeeterb, I want to share with you my transistor tutorial:
**broken link removed**
I think it can help you to summarize basic transistor knowledge.
Hope this can help.

 

[BaCaRdi]

Let us know if you need anymore help. That tutorial posted is very good, you will get allot out of it I am sure.

-BaC

>>main circuit loses power, turning on or Off LEDs

I want to use transistors in my control circuit, but am at a loss as what connects where. I need in my circuit diagram transistors to act as switches. How would I connect them if I wanted them to switch when one section of my main circuit loses power, turning on or Off LEDs. The way I want it, the transistors will switch when there is a loss of current going between the two posts of the upper or lower water level sensors, thus activating each individual LED or series of LEDSThis is kind of an offshoot of the thread Control Circuit help. I have established the main portion of the circuit and now I want to be able to control the indicator circuit that I have also designed, with the aid of my fellow members here on this forum. . I've been redesigning the circuits using PCB Artist and have compacted the circuits to a much smaller area. I just can't figure out how to output them in an image format that can be posted here.

 

[gramo]

Just in regards to the OP's use of a switching device, have you considered the **broken link removed**? It allows you to control 7 channels with a single chip and only requires a common earth. Handy.

Internally it looks like this
**broken link removed**

A Logic High (5V) will "switch" an earth to the relevent output, eg

**broken link removed**

They are cheap as chips too, and like I said before, they are a single chip solution for switching devices

 

[skeeterb]

Heres a link to the page I used for my circuit. http://www.kpsec.freeuk.com/trancirc.htm#inverter it fits what I need for my circuit because the output of that section of the circuit is opposite of the normal output of that type of circuit. Hopefully this will work for me.

@Gramo

I didn't want to use any more ICS like the 4011 and 4093 for the simple switching that I needed for my indicator circuit. But thanks for the advice though.