profile cutter

I have been working on a profile cutter for a while now. Part of the mechanical section has been completed. So I think it would be prudent to see if I can build the electronics section to control the movement. I’m hoping that someone out there may have some advice or may find a fault before I embark on this project. all comments are welcome.


I know the opamp section needs more components to function as a saturation switch.
This section will be interfaced with transducer (photo diode) which will trace a profile drawn on a piece of transparency.
As the optics move to the dark section, the opamp will saturate to the negative driving the pnp transistor fully. The zener diode will conduct as soon as it passes the threshold and this will switch on the pnp at the top which will switch half of the H bridge.
The same will happen when the optics moves to the light section of the transparency but in the other direction.

You might search here and the internet for line following robots.
Do you need bootstrap for the high side drivers?

thanks

If you mean by boot strap, the resistors that ties the gate to the ground then the answer is yes. Because I found that not tying the gate to the ground resulted in the mosfets switching on erratically. And it also helps in switch of time.

can you recomend a simulator . preferably a freeware. and something graphical. i would prefer not to write code, instead draw the circiut and then simulate.

**broken link removed**

realy nice ,thanks so much

The circuit seems to be working in the simulator. Can someone review and let me know if I overlooked something?
The circuit will be used on a profile cutter. Basically it’s supposed to control a motor by following I line printed on transparency. The signal-generator will be replacing by the sensor in the actual circuit. The signal from the sensor is fed in the opamp which will saturate in either the negative side or the positive. The next stage will produce a low impedance output (I was hoping to create some delay here with the zener diodes) which is then sent to the H bridge (one side is inverted).
Any view will be highly appreciated.
Thanks
And thanks again Jumides for the simulator

How accurate are you hoping to get your profiles cut ? The circuit does not have any compensation for 'dither' so the head may do a lot of hunting for the line edges.

circumvent the dither proplem

Do you have any idea how I can circumvent the dither proplem?

You could slow the response with simple RC on the input to the op-amp. However, I would suggest using a PIC or PWM to drive the motor.

I’ve just started with pic.
But I understand tl494 pretty well. So I can use that in the meanwhile.