transistor switch help

finished the layout but very not happy with it! loads of things i will change on the mark2. still it will do for now and i can replace later, but this one will get me in the race also having trouble getting the pcb image on the pcb!!doing everything normal but not working!!! need to take calm approach later and try again!


forgot to mention as this one is so crap there is NO copy write on it lol

i used all 11 sheets of that expensive release paper designed for making pcb's and didnt get close to a single board i could use!! so i went back to the old method and used the paper recommended by my friend Eric Gibbs (argos catalog paper) and bingo first try as always a board i can use, this one isnt perfect tho a few places would need a tiny touch up (if i had a marker pen!) but they are tiny and i only spotted them under the scope, main problem seems to be the knew laminator is same model as the old one but dosnt seem to get as hot i am not allowed to tweak it tho its a GBC heat seal H312 so if anyone knows this model and has a tweak for it

etched board, it came out alright (not perfect but pretty good), next time i will watch the distance between traces as some are scary close to each other! also standard pad sizes in proteus are silly small hence why i changed them to square ones next jobbed is to drill it (yuk) this really p's me off as we have a hugely expensive cnc milling machine that cost £££££ and its not been used once!!! two years old and never used! grrr truth is we dont have any mill bits and dont have a clue how to set it up or use it!! its a A3 bed one, one day i am going to try and hook it all up and get it to drill my boards for me!! but first i got to get dad to move it into the outside workshop (its in a shed at the mo) it dosnt fit in the house the removal men couldnt get it through the doors. not sure how we going to move it as it took 3 of them to carry it! dosnt look that big but its heavy, i will take a pic of etched board soon as i have found dads camera! its gone missing from the workshop so dad has probally walked off with it

Little Ghostman said:

next time i will watch the distance between traces as some are scary close to each other!

Click to expand...

If you think they're dangereously close you can trim them with a utility knife.

i have trimmed a couple now, i think maybe the toner squashes a bit when it's in the laminator, i will have to try and allow for that in the future.

Little Ghostman said:

i have trimmed a couple now, i think maybe the toner squashes a bit when it's in the laminator, i will have to try and allow for that in the future.

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You can also try to avoid acute angles, such as the one next to Q8. They sometimes do not etch well. I always try not to turn traces more than 45 degrees.

Little Ghostman said:

i have trimmed a couple now, i think maybe the toner squashes a bit when it's in the laminator, i will have to try and allow for that in the future.

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hi L,
If you are not 100% sure of the accuracy of the artwork, a simple check is this:>

BEFORE assembling the PCB, connect the DC power supply to the power input pins.
Set the power supply to the required voltage and set the current limit to say 20mA BEFORE you switch ON the psu..

Using 0V as the reference point for your voltmeter, probe ALL the expected +Vsupply points on the PCB.
You should get the correct voltage reading.
then try some other areas of you PCB where you would not expect the Vsupply to be present.

Doing these simple checks can minimise destroying components when you first apply power to the final assembled PCB

E

no excuse but it was a rush job, i will post a pic of the etched board soon as i can get the camera, that trace by Q8 was ok in the end but its a fair comment, looking at the actual board i have been lucky in a few places. it will definitely get redone soon as i get time, there is alot i can improve on it. oh well its all a learning curve, it saved me short term time to meet a deadline but long term it's going to cost more time to refine it and improve!
working on a simple (well was meant to be simple) rs232 board for a couple of things i am doing including the incubator. its not a critical board for the incubator to start with so i will take a little more time on it.

ericgibbs said:

hi L,
If you are not 100% sure of the accuracy of the artwork, a simple check is this:>

BEFORE assembling the PCB, apply the DC power supply to the power input pins.
Set the power supply to the required voltage and set the current limit to say 20mA BEFORE you switch ON the psu..

Using 0V as the reference point for your voltmeter, probe ALL the expected +Vsupply points on the PCB.
You should get the correct voltage reading.
then try some other areas of you PCB where you would not expect the Vsupply to be present.

Doing these simple checks can minimise destroying components when you first apply power to the final assembled PCB

E

Click to expand...

great one eric! another for the book i have looked at it under the scope and found a couple of really tiny places where the enchant wasnt left long enough and i have had to slice the slither, but to make sure i will do as you suggest! nothing worse than drilling loads of holes only to find the board dosnt work! and you cant see the error on the trace

ok got some pics! keep in mind i havnt made a board for well over a year and havnt made that many before anyway! also the pics are taken at hi mag so you can see fine detail of tracks even the tiny scratch marks from cleaning off the toner lol, also note that the bad corner by Q8 actually by some miracle came out fairly well

It looks very good!

I've had time to look over your board. I'm going to support you on Q8, it has a turn on the base in Pic 3, I'm not sure if electrons care if it's on that angle or not? If this is your concern, there was plenty of real-estate to do it? Again, I'm not sure of your concern. I did see some cut or clean marks on Pic4, no big deal either. I like it

If there is an electrical reason that it might be a problem, else I don't see it.

most te marks are cleaning marks, they look bad because i took hi res pic at hig mag then zoomed in a little more on the pc and did a screen capture to post. i think the concern with the tight corners is more that normally they dont etch well, the reason for redoing the board at a later date is solely because most of the Leds are not where i want them and the board could do with being smaller.
the biggest traces apart from the power ones are 40th with some 35th's.
having seen how much they squash out (ok is a fraction of a mm) i will allow for this on some the other boards because i need to do 3 boards with 80 pin pics (tqfp), traces from the pins would normally be around 10mil but i will probably go with 8 for pin tracks and pads, and let the squash widen them by 2mil . the board is ok and i think fairly good considering i havnt done one for well over a year and only done 15-20 boards before but it isnt as good as i want it .
i cant believe i got through so much that special paper without a single nearly ok board! and simple argos catalogue paper gives you a useable result ike that straight off! also i leave the white residue on the toner once i have taken the paper off, i think it helps if you have to use a marker pen in places, i used one in a couple of tiny spots, the one i use is a freezer pen and works great as a resist pen! the enchant is that really highly concentrated feric chloride (40% i think) watered down by about 30% and then sat on top of radiator and i just gently rock it back and forth, took around 11 mins to etch, i thought because of the scratching from cleaning i would get some undercut but that dosnt seem to have happened

I think in the future you should protect yourself by making a chemical hood. Vent the gases up and away from you. Heres on someone made, it doesn't have to be the same it, could even look like a sandblasting box. The just pipe the fumes up and away from you. You don't want your head just above it, breathing it in.

killivolt said:

I think in the future you should protect yourself by making a chemical hood. Vent the gases up and away from you. Heres on someone made, it doesn't have to be the same it, could even look like a sandblasting box. The just pipe the fumes up and away from you. You don't want your head just above it, breathing it in.

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thats a really good idea!

I like the second one better, but I think it should be more on an angle, like the professional ones. An old dryer blower and tubing should work ok for the vent pipe.

Even an old cooktop hood would work if you modify it.

second is better, also as we are (ok as dad is) ripping out the kitchen there are some kitchen units one in particular that would make a good box like the second one, we have a old bathroom extractor and some flu liner from just having a wood burner installed that just leaves finding some acrylic for the front! i might get dad to make a frame for some old green house glass we have, and a small mod to make the front bit on hinges so it can be lifted up for bigger stuff to go in

From source 12V delivered to Q2 Transistor that’s a large
signal gain. Transistor switch are known as the Saturation Region
and the Cut-off Region in operation area. Approximately 5$ or less for combined Ckt components adjust cost.....

remon7 said:

From source 12V delivered to Q2 Transistor that’s a large
signal gain. Transistor switch are known as the Saturation Region
and the Cut-off Region in operation area. Approximately 5$ or less for combined Ckt components adjust cost.....

Click to expand...

i am sorry but i dont understand what you are trying to say there?
I will get LG to post the new board as there have been a few changes, actually i have given him a couple more weeks to finish the project as we hit unforeseen problems that are going to require him to almost completely redesign most of his incubator!

ah i see thanks mate