Parallel Port 3 Axis CNC Driver, Opto-Isolated, Unipolar Steppers

Step 5 MOSFETs and 7805

Find the 7805, its in the same package as the MOSFETs but is labeled "7805"

Its place is labeled IC2 in the illustration. The metal tab lines up with the black part in the illustration.
Solder in securely, and make sure that the center pin has a really good solder joint.

Then starting from one end, place and solder the MOSFETs. See the top-side illustration and align the tabs on the MOSFETs with the black part in the illustration.

note: The tabs on the MOSFETs must not touch, as the tab is probably tied to the drain and it will not function correctly. There should be no need to heat sink the FETs.

Comments

[dablakh0l]

I just noticed that R20-R25 in the layout do not match their placement in the schematic. Is the schematic needing to be updated to match the PCB layout?

Thanks.

[ChromationSystems]

I am aware of that, I wanted the resistors in numerical order on the PCB. It would have been to much work to go back and re-name all the resistors to coordinate with the order on the PCB's silkscreen layer. 

Just know all resistors going to the MOSFETs are 1kohm, all the rest are 10kohm, excluding the resistors nearest to the DB-25 connector. or place as seen in the silkscreen layer.

Sorry if it has caused problems

[flothmann]

Hi great pcb, please just consider add some HEAT SKIN (just a piece of aluminium) to prevent mosfet damage caused by overheating (when the current pass throught the power elements like the MOSFET´s are )

[ChromationSystems]

 My motors run at 24v @ 600 - 800ma, even when ran for hours the MOSFETs don't even get warm. Most of the motors are off at any given time, and since only 2 MOSFETs could be on at any time ( full stepping ), each MOSFET is only subjected to a maximum of 50% on/off cycle. Plus the FETs i used are 60 watts, a heatsink is needed for that much, but 10 - 30 watts at 50% cycle won't create to much excess heat. But a they should be checked by touch until it is known weather they can handle the current.
Also each of the MOSFETs tabs can not touch, as the tabs are connected to drain, and would interfere with operation if multiple FETs had a common drain.