Newest Threads

Rbeckett · 05-20-2012, 12:38 PM

For the prototype boards I am building what method do you guys think will provide the most flexibility and repairability? I have a large supply of .1 pitch perfboard and a good supply of vero board so it is just a matter of choosing the connection style. I am thinking wire wrap may be batter than point to point soldering in case I want to change a component or circuit without trashing a board and having to start over with placing components. Any signifigant negatives to this approach other than being time consuming and error prone if you get in a rush? Thoughts and Comments? Thanks for looking and joining the discussion.
Wheelchair Bob

Rbeckett · 05-22-2012, 11:16 AM

I can't imagine that no one has not waided in with at least one opinion. I think that as this projects evolves, maybe a seperate board with IDC connectors is gonna be the way to go. Have each major function or circuit on it's own board and connect it to the MCU as a plug in or shield type of set up. The neatly routed and zip tied point to pont wiring with proper attention to color coding will work very well for developement and prototyping. If I let the magic smoke out it will also be on a smaller scale with less components to recheck and replace if damaged. Thinkin out loud again, I still have plenty of time to decide since I am still waiting for Chinese customs to release my stuff. Too bad they are so inconsistent. One shipment in 9 days another is now over 30 days, no rhym or reason. Oh well that was part of the bargain when I started the project, so nothing lost, so far. Still looking for opinions or general comments. Any of the more experienced board builders have a different point of view or take on the proposed solution? Thanks!!!!!
WCB

Brewer Gerard · 05-23-2012, 11:26 AM

I'm currently moving house so my project is on hold. I was in the middle of trying to use an ultrasonic distance sensor to determine volumes in my HLT. All my prototyping so far has been initially done on a prototyping breadboard and then soldered onto veroboard. I did consider those copper square pad boards and doing wire wrap for the connections but that would mean IC sockets for every component so i said sod it!

Any more detail on yer project?

Rbeckett · 05-23-2012, 12:40 PM

Brewer G,
Just started drafting out the circuits and doing the resistor and cap calculations. I started with the simpler stuff first in the schematic and will progress to the PID interface and thermocouple amplifiers as I add to the diagram. Most of the stuff i have drawn so far is straight forward drive a relay to operate a solenoid and do it at TTL voltage. The solenoids are 100 VAC so I am using the smaller 25DA SSR's for those. Not much else really happening, too hot for me to be out in the shop, so I have been trying to draw the schematic and continue to study the intro to 16f877A microchips and C entry level programming. My brain hurts, but I'll get it sooner or later...
WCB

crane · 05-23-2012, 01:46 PM

When I develop small things I start out on a breadboard for proof of concept. That allows you to change things up quickly. Once I get the circuit sorted out I then move to protoboard and solder in point to point.

crane · 05-23-2012, 04:53 PM

If you are planning on building your own amp for thermocouples here is some info that may be useful. I spent some time at work improving the amp circuit we use for our thermocouple sensors. We started with the opa2379 opamp but switched to the opa2333 because it has zero drift and much lower offset voltage. We use a basic diff amp circuit with a voltage bias of 1/2 the ADC's Vref. The amp has a gain of ~30 and uses resistors with 0.1% tolerance. Even with the better opamp and tight tolerances on the resistors we still get error that needs to be accounted for. To do this we do a one time calibration in manufacturing by shorting the input to the amp and sampling the output. Each time the thermocouple is sampled we subtract the calibration value from the measured value to correct for the amp's error.

**carlisle_bob** · 06-03-2012, 07:39 PM

Hi

A lot depends on what you are using for parts / trying to do. For analog stuff - wire wrap is somewhat painful. For a mass of TTL gates it works pretty well. Most of what I do gets done up on prototype board(s) and then shot as a pcb. There are a lot of cheap places to get small runs of double sided pcb's these days.

Bob

Rbeckett · 06-16-2012, 12:00 PM

CB,
The point to point soldering is a real PITA. it's very hard to get the solder to form a track on the back of the board between through holes. Wire wrap or some variation of it is probably going to be easier and less prone to errors and shorts. Did a few practice boards and what a PITA, plus the posibility of overheating the components on the boards. Let ya know how the wire wrap hybrid approach works after a couple of test boards too.
Wheelchair Bob

crane · 06-17-2012, 02:25 PM

Wheelchair bob, solder isn't meant to bridge gaps. It is actually meant to do the opposite by whicking up the through hole. I have tried this before too and got frustrated quickly. I use the extra lead from through hole components as a trace to connect over to other pins on the backside of the perf board. For long runs or components with real short leads I will use bus wire. I also have some bus wire insulation to prevent wires from shorting to each other. I can get the PN's for the bus wire and insulation I use once I get out of bed.

Here is some pictures of my brew control breakout board that plugs into 1 of the expansion ports on my microcontroller. I have a PFET to drive my SSR with an LED to show when it's on. I also have a dual opamp to subtract off the wire resistance for 2 separate 3 wire RTDs.

**carlisle_bob** · 06-17-2012, 02:52 PM

Hi

These guys:

http://www.4pcb.com/barebones-pcbs.html

Will do an overnight PC board run for less than what you pay for the wire wrap base board. You also don't have to pay for all those wire wrap sockets....

For about the same price as the wire wrap base board and a handful of sockets, they will do a $33 board in a couple of days that has solder mask and silk screen on it.

http://www.4pcb.com/33-each-pcbs.html

Unless you have a major inventory of multi colored wire wrap wire, figuring out which wire *actually* goes where when you are done is more of a hassle than following a trace on a pc board.

Yes indeed you do need to layout the pc board. The software is free, it's fairly easy to use. If you are dealing with the sort of stuff that you would wire wrap, it's pretty straightforward.

In both cases (bare bones and $33) you want to lay out one board you can use for several things. Depending on what you are doing that may or may not be practical.

There are a *lot* of other places doing the same thing. Some with better prices. I've used these guys a lot and never had a problem with them.

Bob