Well despite your pessimism I am not going to give up just yet
1. My aim is to create something modular so you can use the modules to make a single, two, three or four channel PSU, just keep adding the modules and the transformers. I am designing the PSU module to work from a single secondary winding so you can use low-cost off the shelf transformers - remember, just like you can pick up these PSU's for $300 (which by the way if you know of any would buy a couple more at that price), as a DIY'er you can also pick up transformers cheap. If CATII/III isolation is important then you can always use one transformer in the box.
2) Yes of course you are right I was not thinking of the meter, the ADC chip will be the most expensive part by far, I think a decent dual ADC for this resolution will be $6-8 a piece. I have not done much with high resolution ADC's, its something I need to play around with, I was thinking of something like a 16bit decade counter chip in conjunction with one of the the MCU's 16-bit timers would give me a 24bit counter, I fancy having a go at a dual or multi-slope implementation in software. Failing that, there are off the shelf ADC's that are high enough resolution for not so many $'s a pop.
3) This is one area where I don't see much point to be honest. GPIB is an old standard, it belongs in the dark ages of the centronics parallel port and there would appear to be less and less support for it as serial protocols like RS232/485, USB and in particular ethernet seem to be much more current, especially since SCPI is supported over these. That said I am well aware that GPIB is still in widespread use for test automation etc, I don;t know that much about it so I can't really comment on it apart from it can not be so hard to implement, its really just a parallel bus of some form. This is certainly not on my list of priorities but if I get some time I may look into it as an academic exercise. My thoughts are with RS232 (simplicity) and Ethernet (TCP/IP) because anyone can plug in and make use of it.
4) Enclosures are a whole different problem, something that would be great to solve. However, what I am trying to achieve is the electronics, for s DIY build the enclosure and heatsinks would be left up to the builder to accommodate.
5) Yes, they are cheaper than most other IC's nowadays so not a problem, in fact anywhere I can replace a chip(s) with a CPU it will save time and money (GPIB and their custom chips spring to mind, I think a decent PIC could possibly run a 1Mbit parallel buss).
6) I too like VFD's very much, but as you say they are expensive so not accessible to everyone. Of course I am trying to make something that is modular so there are options. For those of us that could get a VFD for cheap (I recently bought some 64x256 graphics ones for £5 each) then its an option, for others a "stupid LCD" might be acceptable....
Apart from the fact that I am not actually trying to go into production and compete with HP, the point was really to create something that is every bit as good (spec wise) but on a DIY budget - maybe I can and maybe I can't but I am still going to try
The precision op amp used in the HP slope detector is about $5 at a one off price from one of the most expensive R&D sources, they go down by 50% at a quantity of 100 (
http://uk.farnell.com/analog-devices/op2177arz/op-amp-dual-precision-smd-2177/dp/9994238?whydiditmatch=rel_3&matchedProduct=ad706&matchedProduct=ad706&whydiditmatch=rel_3) so not too bad, but there are plenty of other more modern devices that are even better and cheaper.
I was not thinking about advancements in regulation specifically, they are what they are, what has advanced is the components you can use to create the thing and all of out control circuitry around it.
You obviously have a very strong conviction that this can't be done which is fine but I am still going to try, there is nothing like finding out for ones self!
Home
Help
Search
Login
Register
