Hi, Can anyone please make me a Gerber file so I can get a tiny PCB made. I have someone that can make it but they want the file.
Basically 2 x 4K7 .5 watt resistors. One in series and on in parallel.
This is for access control doors that we keep twisting wires and resistors together and they are never tidy.
If any one can my email is duncan@watchu.co.nz
Thanks in advance
It needs to be as small as possible. Thanks
Lets assume you find someone willing to make you a pcb. (Not very likely if you do not even mention that you are prepared to pay)
Then they would at least need more details. What is the exact order number of the resistors? How does the board interface with the rest of the world (ordernumber of the connectors if reqired)? Where do you plan to order the board with which options? (What are the restrictions for the pcb?)
Lets assume that I am willing to pay. I don’t mind if someone is able to actually make the product for me. hopefully it will be as small as it can. I only want about 100 units to start with, hence it’s not a big project. I could make them myself if I have the tiny breadboards. I just don’t know where to source them. Thanks
He wonted 0.5W resistors. May be he needs some level of immunity to surge pulses.
@Piotr: You are right, I probably shouldn’t design random stuff, without any real specification. I just used all the given information:
For everything else, I used my imagination (in doubt the fastest solution). Maybe this gives @watchu an idea why everyone is asking for more specification. I wouldn’t be surprised if my example is “too small”.
I agree with you. Probably it is the right solution.
We have no info about that someone that can make for OP the PCB.
I would be not surprised if there will be some minimum dimensions accepted so may be the gerbers should be prepared for panel with several such PCBs.
Do you mean accepted by the board manufacturer? Our smallest one is 5.3x7.5mm. No problem whatsover with JLCPCB or PCBWay without panelization.
No problem to get 0805 in 0.5 watts even as automotive standard.
Voltage rating might be an important parameter. Its a bit different if it only needs to work with 24VDC or if it needs to be for 220VAC.
Another one is the rated temperature.
Those ratings go on top of the requirements of course.
It was fast answer. I supposed what I see were 0603.
I use one 100 ohm Pulse Proof 0805 resistor (80W/50us).
I suppose OP had in mind THT resistors.
Yes.
My PCB manufacturer - if I place a production order they can do all panelization themselves, but for prototype orders the minimum PCB size is 30x30mm. So when I have smaller ones i made a panel of themselves.
We completely don’t know who is under:
And at the other end of the spectrum, I’ve gotten 0.25" square boards (6.35x6.35mm) done without issue at OshPark (I remember I had asked what the minimum board size is, but I’ve forgotten what I was told). The OP needs to find out what the minimum size is from the planned board manufacturer.
I’m not trying to 2nd guess your needs, however I think you might be wise to add a capacitor in parallel with the resistor that is connected to:
“device common” and “device normally closed”
Having the pads there even if you end up never using it is worthwhile If you can afford the room.
John
In order to reach the 0.5W limit, there would have to be about 48V across each resistor. Are you working with that kind of voltage?
The reason for using higher power elements comes not only from maximum DC power possible.
It can be for example:
OP write about using it in access control. Access control EMC disturbance resistance specification are higher then for domestic use. These resistors are outside of transil protection used probably at device entry and connected to wires (we don’t know how long).
They could be exposed for example on disturbance during lighting near the installation, we should also assume potential attack on access control not only by using crowbar.
In about 1997 we had something about 100 installations of our access control system all over the Poland. We used current-loop connections up to 1200m long. It happened one installation that each spring and autumn during storms our devices liked to hang-up (it not happened during each storm but happened once or twice a year). Resetting them was enough but I asked to not reset but call me.
I disassembled the magnetic card reader being all time powered to try to find the reason of hanging. And I found. Then I start to collect all materials about surge protection as I knew nothing about it before. Internet was not so full of information than nowadays so it was not as easy as today.
The end effect of my interest can be sum in the mail we received once from one our installer saying something like that: “The thunder strike directly at building we recently installed your system. They have all alarm systems, local telephone exchanges, and net cards in PCs damaged. But your system needed only be reset. Now others will earn money but we not !”
Somehow I think OP didn’t consider those aspects, or they would have specified those, but I could be wrong. Anyway the requirements are underspecified.
I also think it is not he who considered such aspects. So where from 0.5W? I suppose it is from access control system installation manual. The connection looks like so called parametric input. Being not sure I suppose the voltage here is no higher then 5V. If so, and the resistor power was specified (bigger then 0.1W) so why it was specified. May be manual author considered such aspects.
Of course may be there is no such specification, but it happened just to use 0.5W resitors and copied here the data from last parcel.
I also suppose (only suppose) OP was thinking about THT 0.5W resistors. I would not assume that 0805 (even 0.5W) could always replace THT 0.5W.
You suggested that only maximum dissipated power should be considered when resistor power is specified. I don’t agree with it - so my answer.
Yes - as mentioned by various posts in this thread, the 0.5W requirement may be a case of excessive spec margins, but it may have justifications - either electrical, or non-electrical - other than routine circuit operation. Assume that the customer actually wants what he asked for, until you have evidence that he doesn’t know what he’s talking about.
Dale
P.S. - I hope we haven’t scared off @watchu . The information in this thread may actually be quite useful to him!