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current flow

Hi guys, I have attached a schematic that I am have some trouble analyzing, using Kirchhoff’s current law, how will the current flow through R4 and why is it in that direction?

H bridge

Hi, can someone please tell me what is wrong here. I have attached my schematic as pdf. All the line are physical connections on my pcb. The right tip127 gets hot when I allow current to flow.    


h bridge

Hi, I have been trying to get this h bridge right for almost a month now, ( see attached pdf)


I have a 1K res in front of the opto isolators Collector for current limiting. The opto isolator's LED is powered by a micro-controller. According to my code. When 1 is high 4 is high and when 2 is high 3 is high.


software integration


I need some advice on data transfer; I want to build a 3 axis CNC lath. Where can I find some software that can integrate into Autodesk invertor and send my completed drawings specs to the laths control electronics? Will I be able to use parallax microcontrollers on the lath?



I need some advice on how to draw up the schematic for a series B female usb, i need to connect to a BS2 IC, and my pc does not have an RS 232 port. Can i just make the connection on the PCB or do i need any components between the ubs and the ic’s programming pins.



I need to build a receiver and transmitter for a set of Motorola TLKR-T7s. the transmitter and receiver is only required to over come a mountain blocking the signals from each other. I only need to transmit 2.4 km with it. I want to place the receiver/transmitter at the top of the mountain so to go over it instead of through it.

my first project

It might work, but I am not that much concerned with pressure applied to the given surface. And I can’t use motor amp changes to indicate when the “leg” is in contact with a surface because of inertia and movement speed of the “leg” that constantly changes. My pressure applied so to speak of will only be applied for rather short time periods and would almost constantly differ in pressure.