Some good suggestions. I have been looking into this. Early thoughts, untested, probably has errors so no promises. I don't have a lot of time or skill.m0xtd wrote:Hi Noel,
Comments based on building the MiniTiouner batch for ARISS. Mostly arose from trying to fit everything into a Hammond 1590D box but several are just observations based on the experience of building ten of them
1. Vertical NIM - please, or at least the option to have the NIM vertical. Having the lugs secured via suitable PCB holes would make it a lot more mechanical rigid and remove the risk of the two "legs" on the existing PCB breaking. Note, one thing I did was to bend the lugs on the NIM so that they lay over the PCB legs (P1 & P2) and then soldered both. That way I had a firm earth connection as well as increasing the mechanical strength of the NIM/PCB combination. P2, due to its smaller size, is very fragile compared to P1.
2. PCB Mounting points - at least two, if not one on each corner.
3. Voltage Regulators - I mounted the PCBs inside a metal box and ended up securing the PCB to the box via three nut/bolts which also attached to the voltage regulators. The box therefore became a big heatsink. However, It would be better if there was an option for the regulators to be bolted to the case directly rather than through nuts/bolts.
4. PCB holes for the PSU - might just be the PSU I got (http://www.ebay.co.uk/itm/5-pack-MP1584 ... SwLVZV5Kdc) but the holes are ever so slightly off centre. I used pin headers (0.1") - fitted the PCB perfectly but didnot match the holes in the PSU.
5. Is there any reason for mixing SM and TH components? Can we stick with just one type?
6. The links for the bias voltage - is it at all possible to do these just like the LK2/LK3 links for powering the voltage regulators. Removes the risk of accidently enabling both methods and saves the NIM.
7. Having the I2C bus brought out to the J4 header is brilliant for debuging issues when the NIM doesnt respond but everything else checks out ok. Can other signals be made available?
8. Power socket - not really that bothered by that one as I used a plug/socket arrangement the supply. Connection to the board was via twin cable entering the existing holes from underneath. For me, that meant the only thing protruding from the edges of the board were the USB and NIM connections.
9. The J3 header - going to be difficult to use that with the USB module in situ. Can it be moved to the other side of CN1 if there is a plan to use it.
HTH.
73 - Ciaran M0XTD
1 - yes.
2 - yes - use a fibre washer if shorting close tracks is an issue - or use a smaller nut and bolt. Two per corner is too many. Its one per corner.
3 - Chop off the end of the PCB and you can do this. Its designed as a radiator but its only going to be about 50C per watt. AS dissipation is likely to of the order of 5W that's not enough so proposal is to put a spacer underneath and conduct to the case - thermal vias included..
4 - Redesigned the PSU module to not fit any known board - that way everyone will be equally unhappy. There seem to be many variations.
5 - Sigh
6 - Hmm
7 - All of the USB signals are available on the top of the USB module - so its not all that hard to intercept them for testing!
8 - Plan to use standard DC barrel socket
9 - its nowhere near and no longer called J3.