Basic problem with transistors

[giftiger_wunsch]

I think my problem was that I assumed that the only molex socket they have on their site matched the only molex header plug they have on their site. I compared the the dimensions to the other header, and found it had exactly the same pitch and pin cross section. I just double-checked the data sheets and confirmed that.

But it appears I was wrong about the socket matching the plug. It appears they don't actually sell a match for either the plug or the socket, which is quite infuriating. Though I don't see how their data sheet could be accurate - according to the data sheet for the sockets, they mate with 0.04mm pins, but since they were too large for 0.64mm pins...

It also means I just wasted my money on 7 34-pin headers, 2 5-pin headers, 50 2-way housings, and 100pk of molex crimp terminals.

It doesn't much help either, that the molex housings would be too large to be used with a larger header. The housing would interfere with adjacent pins. I discovered, slightly ironically, that the molex housings are a perfect fit for the 10-pin header on the robotic's arm small circuit board, and the motor cables have similar housings (except more compact and in my opinion, better. They are the basic rectangular variety in black plastic.)

Looks like I'll have to hunt for more header plugs and sockets. It appears I'll need 2-way (or better, single-pin) wire-mounted sockets which match a 2.54mm pitch, 0.64mm² pin, and a double-row 10-pin header with 2.54mm pitch and 0.05mm²? pins.

 

[giftiger_wunsch]

I assume there are no problems with my finalised schematic, so I've been planning the PCB layout (also using powerpoint ) and it's becoming quite complicated... looks like it may be pretty tricky, especially for my first PCB!

Any tips on how to design / produce the PCB?

 

[Hero999]

CAD software is better at making PCBs than PowerPoint.

Heck I should talk, I've used OpenOffice.org Draw to make PCBs, it's hard work but still better than PowerPoint.

I used Altium Desinger (formally Protel) at work and it's great but very expensive. Others here use Eagal or FreePCB, there may be others. I've dabbled with Eagal but never took to it and having Altium Designer at work meant I never needed it. Now I no longer have Altium Designer, I might give FreePCB ago.

 

[giftiger_wunsch]

I've tried Eagle, but I've found its components libraries extremely difficult to navigate. I gave up trying to make schematics, let alone PCB designs...

Unfortunately there is the dim realisation at the back of my mind that once I get this circuit board sorted out and etched, I'm going to have great difficulty soldering it, and once I've finally got all of the joints soldered properly, I'll probably have more success threading a mains cable through a sewing needle than trying to solder my headers onto my prototyping board. The contacts on the board are tiny and I can't even do basic soldering right now. Need a lot of practice before I'll be anywhere near good enough to solder to something as small as the contacts on my prototyping board.

I may have to consider practising enough to do the PCB I'm currently designing, and then getting an expert to solder the header onto my prototyping board for me since that part will probably be beyond my abilities for quite some time

 

[Hero999]

I'll post the footprints I use if you like but I don't know how we'll they'll convert to .EMF or Power Point.

I definitely think it's worth learning a PCB CAD package. I didn't get on with Eagle either, may be I'll give it another go now. What about FreePCB have you tried that? I haven't and I'm willing to give it a go.

 

[giftiger_wunsch]

I haven't tried FreePCB, I'll probably download it tomorrow morning (well, later this morning actually) and see if it's any good.

 

[giftiger_wunsch]

I started the PCB design again using FreePCB instead of powerpoint now, but the range of resistors is slightly confusing, and I'm not sure if I'm drawing the copper tracks correctly. I'm having to use "draw copper area" and make a areas which just consist of lines.

I also can't adjust the width of the resistors, so I can't set a more convenient distance apart to put the pads at either end of the resistor either.


I haven't gotten very far with the PCB layout design in either FreePCB or Powerpoint, but attached are screenshots of both incomplete designs; looks like the end result is going to end up quite complicated. I confused the collector and emitter terminals on the powerpoint design so the left and centre pin connections should be swapped. The grid on the FreePCB image is 2mm²

 

[rikilshah]

I think the ultimate answer to your question is using Optoisolator like MCT2E. Nothing is more secure than this things as Optical Isolation is used.Just Google MCT2E Datasheet...