Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Help converting 0-0.90v to TTL logic levels

Status
Not open for further replies.
A

amando96

Guest
hi guys, i recently purchased a wireless doorbell, that i would like to mess around with and make a remote control.
i am using this doorbell because it has a range of almost 200 metres! cossing walls, trees etc, so on a clear view it must have even more!

right now i noticed that if i press the button the receiver has a pin wich changes it's state almost exactly like i press the button( i press the button 5 secs, the receiver changes its state for 5 secs, if i press one sec, state changes one sec...)

But if its a really short 1/10th of second press, the receiver doesnt change its state acordingly, i have yet to understand the circuitry, but i think it may be a capacitor that takes a while to discharge...

if i cant get the button to change the state of the receiver acordingly i will have to use a ''normal'' digital pin and write my own code, keeping in mind that the minimum pulse is 2/10th of a second.

So it should be possible, but it would be much simpler if i could just serial print/read, than having to make my own comunication system...

Hoping to get comments, especially help on the converting to TTL logic levels, and oppinions on this project, if its possible, or not worth the hassle.
The receiver has a HEX inverter, heard it isnt good for high speed aplications, how important is it to have this HEX inverter? could i just remove it?

i Have tryed using an optoisolator(4N35), but for some reason when i tie the wires to the LED inside the optoisolator, and press the button, the resistance on the other side of the optoisolator goes down 8K ohm, is the LEd not getting enough power?
thanks, i've been around this for two days... lol
happy new year!



thank you, and happy new year!
 
i Have tryed using an optoisolator(4N35), but for some reason when i tie the wires to the LED inside the optoisolator, and press the button, the resistance on the other side of the optoisolator goes down 8K ohm, is the LEd not getting enough power?
According to the **broken link removed**, the LED in the 4N25 requires apx 1.2V to turn on, so 0.9V isn't going to cut it.
Depending on the circuit, all you may need is a bipolar transistor, which will turn on with 0.7V base voltage (Use a resistor to limit the current).
You could also use a LM393 comparator for greater noise immunity if required. That way you could set the trigger point and hysteresis to exactly what you need.
There also may be another point in the circuit which gives a higher voltage swing.
 
Last edited:
yes there is, in another area the voltage goes from 0.50, to 3v, but whenever i use that line, even just connect a transistor(2sC945) it somehow shorts the receiver... i know the transistor is connected properly. thats why its been hard to do.
i like the idea of the comparator, didnt think of that, i have one laying around, will try.

thank you.
 
yes there is, in another area the voltage goes from 0.50, to 3v, but whenever i use that line, even just connect a transistor(2sC945) it somehow shorts the receiver... i know the transistor is connected properly. thats why its been hard to do.
...

Are you putting ~10K resistor between the receiver and the base of the transistor (to limit the base current)?
 
yes, i even put a higher value resistor thinking it could be that, but nothing happened...
what i'm thinking is to read that analog value with an attiny or picaxe, and convert it to 5v in the code, and have my atmega 328 read it like that. bit pricy though.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top