i am making a PIC16F84 serial servo controller, but all crappy maplin had was PIC16F84A, they said it was the same thing so i got one but it doesn't seem to be working, the site i saw it on says it is for a ordinary 84 which brings me to the question, what is the difference?

 

The data sheet from Microchip Technology should make it clear.

What's not working?

 

All questions of this type can be resolved by consulting the datasheet. Can you be a bit more specific about what does not work? Like do you have an aaplication that works with a 16F84 and not with a 16F84A.

AFAIK the A version has improved electrical specifications, but is otherwise compatible. Consult the datasheet, that's what it is there for.

 

the data sheet just looks like a load of graphs and random numbers to me.
with the serial servo controller, the servo motor just moves randomly around, when you send the information via the serial port to it nothing happens, i have re done it on bread board so i dont ruin the parts soldering and resoldering them onto the strip board, there is no real correlation between what i input and what moves the servos, it is just random positions it moves the servo to, i am really lost :s

 

Are you building your servo from an existing design?

hgmjr

 

this is the site where i made it from
http://www.rentron.com/SerialServo.htm

 

Just wondering. Did you download the program into the PIC?

hgmjr

 

yeah i did, the servo motor does move, it is just random though, do you want me to upload a pic of the setup?

 

Sure. It might give us some ideas.

hgmjr

 

it iws not allowing me to upload pics, do i need to supply voltage to the DB9 connector? cause i have heard something about supplying power through pin 9 :s

 

Have you gone through and double checked the wiring? Also check the quality of your connections.

hgmjr

 

it is done on bread board so i havent soldered it and i am almost certain it is wired correctly

 

I suspect that the reason that you were unable to post your jpeg file of the prototype is that the size of the picture exceeded the max file size of 293 Kbytes. Can you reduce the resolution of the picture and try attaching it again?

hgmjr

 

i dont have any way of doing that
the ceramic resonator says 400, does that mean its a 4mhz one?
also what does bau rate do?

 

It is a 4 MegaHertz crystal.

The bitrate is set by the program to be 2400 bps.

hgmjr

 

I'm surprised that the design does not include an RS-232 interface device. I think that there may need to be an inversion in the line that may be lacking in the circuit you have.

hgmjr

 

ah i think it works now, i think i just needed to set the baud rate in the program they made, although every few times i set it to a different position it wiggles around a random position then after a second of wiggling it goes to that position

 

The 22K resistor is a good precautionary protective measure to keep the negative going RS-232 input to the PIC from damaging the PIC.

If you have a diode like a 1N4148 or 1N914, I would connect it to pin 17 of the PIC. The diode will better protect the PIC input and clamp it so that it will not go negative relative to ground. The cathode should connect to pin 17 and the anode would be connected to ground.

hgmjr

 

we don't really keep diodes, we don't use them very much. the only diodes i have are LEDs, thanks for all your help so far!

i have tried to make my own application to control it but it does not work, what they are telling me to send via the serial port

 

the data sheet just looks like a load of graphs and random numbers to me.
with the serial servo controller, the servo motor just moves randomly around, when you send the information via the serial port to it nothing happens, i have re done it on bread board so i dont ruin the parts soldering and resoldering them onto the strip board, there is no real correlation between what i input and what moves the servos, it is just random positions it moves the servo to, i am really lost :s

Actually you need to read the text. Looking at the graphs comes later.
Here is the side by side comparison from the microchip website which you could easily have found for yourself
http://www.microchip.com/stellent/i...eId=2533&product1=PIC16F84&product2=PIC16F84A
The change in flash memory technology let them put more words on the die so you went from 1K words to a really crappy(your words -- not mine) 1.75K words. some people just don't know when they are well off.