When&What to use...!!! simple questions?!

[sporker]

Does anyone know any answer to some quick Q's for me?

1) When do you have to use a serial controller like the Maxim232. Is it always neccesary to use USART?

2) What’s the best device to "drive" a TTL signal from a pic chip? Are there any chips out there that will accept a variable/noisy/crappy signal and output a nice clean, powerful, crisp +5V signal? Or should this be a "buffer"

3)What’s a good way to use one power supply and separate it into 2 power sources? In a current project of mine, I have a PIC chip controlling a H-Bridge. I would like to use one power supply for both devices, but the H-Bridge puts lots of noise into the circuit. I need a way to isolate them. I was thinking about using an optoisolator, but am not sure if it will pass noise through it as well.

Thanks so much!
Alan J Jurim

[Sharky]

1. Have you read the PBP manuel HSERIN? Have you been reading the datasheet for MAX232? Have you been reading something about the RS232 Standard(EIA232)? If not try to search the net, here is a link to start with:
www.engr.uky.edu/~jel/course/583/labs/lab6/rs232std.html

2. I'm not quite sure that I understand what you mean, but could it be a Schmitt Trigger that you are looking for?

3. How do you know that you are having a noise problem, do you have some failures that indicates noise problems?



Regards
Gert K.

[sporker]

I have read many datasheets about MAX232 but my true questions is: What is the advantage of using it? In other applications I have not used it and have has serial comm. work. Why add more to my work??

In the second issue, specifically this is what is happening. I want to setup a IR receiver that would give "momentary" control over an electric motor. When the IR decoder receives a signal from a button being pressed and held, the test circuit is really turning the corresponding control port on + off really fast, instead of just on. So this is where im getting that crappy, sort of on w/noise signal.

I know I am having noise problems cause when my motor initially starts, its put reverb back into my whole design but maybe after 1 sec it goes down and it works. This is why I want to somehow isolate the motor ground from the rest of my design to help "clean up" the remaining part.

Thanks for any input,

Alan J

[Dwayne]

Hello Alan,

Alan>>I know I am having noise problems cause when my motor initially starts, its put reverb back into my whole design but maybe after 1 sec it goes down and it works. This is why I want to somehow isolate the motor ground from the rest of my design to help "clean up" the remaining part.<<

Put 2 diodes opposing across the Positive and negative of the motor... That will quite the noise down considerably. The diodes will help take care of the "spikes" and noise of the motor. If you are using a Mosfet, it will greatly reduce the heat/power needed by the Mosfet.

Dwayne

[BigWumpus]

Using the max232 is a simple and safe way to convert the signals out of the pic into RS-232-compatible signals (including inverter!). There is no MUST, but it is the most used way ...

I prefer to use the hardware-UART inside a PIC for receiving data, because it uses not so much CPU-time. You can receive fast messages at high baudrates. And setting up the sender in hardware is very easy....