needing some help - Page 1
Forum section: electronics / projects

author: m3vuv
author_rank: Super Contributor
timestamp: June 12, 2019, 10:09:50 am
content: hi all,ive been trying without any luck to get the attached schematic onto a pcb layout ready to print without any luck so far,would it be cheeky of me to ask if someone can do it for me,im on a time limit with it,all resistors are 2 watt and the first two transistirs are to39 footprints,the blockind diode is mounted off board,cheers paul,btw the pc board i have is 7cm x 10.

author: m3vuv
author_rank: Super Contributor
timestamp: June 12, 2019, 10:10:52 am
content: forgot to sat the relay will be mounted offboard as well as the 2n3055.

author: MarkF
author_rank: Super Contributor
timestamp: June 12, 2019, 10:44:09 am
content: Is the "blockind" diode the 100A diode at the top?I don't see that any of the resistors need to be bigger than 1/2W.Is this your design? It's not good to put two diodes in parallel.What is the coil? What size is it?What is the capacitor? Radial/Axial, hole spacing?The parallel resistors 4K7 and 680 could be combined into single resistors.Is the max voltage 24V? Is this AC or DC? Is the fuse off-board?Mounting hole locations and size.How do you intend to connect all the off-board parts. Connectors, terminal strips, solder to trough hole, etc?

author: OM222O
author_rank: Frequent Contributor
timestamp: June 12, 2019, 10:55:10 am
content: What is exactly your problem? It shouldn't be an issue on a double sided board. Is your pcb single sided? There's too many details missing ...At least specify all the footprints for the components

author: MarkF
author_rank: Super Contributor
timestamp: June 12, 2019, 12:40:41 pm
content: Your circuit does not look right.But, here is half of the circuit without the needed information. PCB 70x70mmThe relay could fit in the upper right corner (depending on size).

author: m3vuv
author_rank: Super Contributor
timestamp: June 15, 2019, 10:04:11 am
content: the bfy51 is a to5-3 case style the other small transistor im going to use is a bc 108 t0-18 style,the stud diode is going off board along with the 2n3005 ,the blocking stud diode is at the top of the schematic,for the cap i want to use a radial lead one,for the relay i just need some pads to solder wires to as it will be off board to.,regards m3vuv.,lastly the field coin resistance is about 9 ohms.

author: MarkF
author_rank: Super Contributor
timestamp: June 15, 2019, 11:38:34 am
content: Let's get some identifiers on the board. I don't know which parts you are referring to.I can't figure out what this thing is. Any description would help.Can R4 and R8 be combined? Can R3 and R7 be combined? Is something else feeding into the bottom of R8?It is not good to have two diodes in parallel (i.e. D4 and D5).Is this a DIY PCB you are going to photo etch or are you going to have it made at a PCB shop? (i.e. Do you want a single layer PCB?)The more parts you can fit on the PCB the better. Is there a reason you have half the parts scattered off-board?It is not enough to say the cap is a small radial one. There are different lead spacing, lead diameter. It would be best if you could give the exact part number or at a minimum the exact dimensions of the PCB footprint. (Pad size, hole size, hole spacing). This info is needed for all parts. For off-board parts, you need to provide the pad size and hole diameter for the wire gauge you are using. Do you care which side of the board the wires come off of?Is that a car alternator? Does it put out DC voltage?

author: MarkF
author_rank: Super Contributor
timestamp: June 15, 2019, 12:12:25 pm
content: Is this your relay? It could be soldered directly on the PCB or its socket if you have one.

author: soldar
author_rank: Super Contributor
timestamp: June 15, 2019, 01:34:52 pm
content: Quote from: m3vuv on June 12, 2019, 10:09:50 amAs a courtesy to others please use descriptive titles. Don't make people open the thread just to find out what it's about.

author: dmills
author_rank: Super Contributor
timestamp: June 15, 2019, 02:55:40 pm
content: Pretty sure your relay is very, very wrong on that diagram (You show a contact where I am almost sure there should be a coil).With a 6 ohm coil and the thick end of 30V your worst case power in the transistor is at a speed where the regulator is also appearing as 6 ohms, so current is about 2.5A, and voltage dropped is about 15V making ~40W in the transistor, which is going to need a decent heatsink.100A into a 0.7V diode is also not insignificant (Thick end of 100W all up), so if doing this the crude way you are going to be burning some power, but if this is for that steam train job I would guess big heatsinks are not impossible?Regards, Dan.

author: Arjunan M R
author_rank: Regular Contributor
timestamp: June 15, 2019, 03:26:12 pm
content: Quote from: MarkF on June 12, 2019, 12:40:41 pmWhich software did you use for designing the pcb.?I have seenmany peoy in the forum using the same software.

author: MarkF
author_rank: Super Contributor
timestamp: June 15, 2019, 04:41:40 pm
content: Quote from: Arjunan M R on June 15, 2019, 03:26:12 pmI use Diptrace for my circuit schematics and PCBs.

author: MarkF
author_rank: Super Contributor
timestamp: June 15, 2019, 05:32:50 pm
content: I updated the PCB in Reply #4.It is a total WAG (Wild Ass Guess).The resistors are 1/2 W.The 2N3055 in a TO-3 package are getting hard to find and expensive. I would use a TO-247 package if you aren't already.

author: m3vuv
author_rank: Super Contributor
timestamp: June 15, 2019, 09:26:46 pm
content: its going to be a single sided board,the reason the parts ie diode and 2n3055 are off the board is for heatsinking,the circuit is for a voltage regulator for an old br mk1 railway coach,basicaly want to use what bits i have to hand as regards the cap if we have 2 pads say 13mm apart i can find a cap to suit,ive got one built to try,should be going to the railway in the week to test it,couldnt this week due to the rain! and flooding.

author: Arjunan M R
author_rank: Regular Contributor
timestamp: June 16, 2019, 03:10:04 am
content: Quote from: MarkF on June 15, 2019, 04:41:40 pmI use KiCAD.

author: MarkF
author_rank: Super Contributor
timestamp: June 24, 2019, 07:57:51 pm
content: Refer to his other thread on the same subject:https://www.eevblog.com/forum/projects/quote-for-a-job/