Bob,. I've done extensive work in the developing world. A few points a.) this is to be manufactured by the nonprofit I am volunteering for, and not sold, but donated. They(businessmen, doctors, and administrators) chose $8 as what they saw the maximum price that would make it feasible. b.) You're speaking of the US medical community. The hospitals in Tanzania are hospitals you need to visit before you could understand, but I assure you they don't care about the brand of components used. c.) This isn't a device for profit and I'm not worried about the insurance companies because... largely there aren't any there to worry about. ben On Fri, Apr 3, 2009 at 11:32 AM, Bob Axtell wrote: > I guess I'm just not getting this. No offense is intended here, but > you might consider getting a medical consultant before you waste too > much time. What I have seen so far indicates that > you might be in over your head. > > Some folks here have tried to be gentle. I will be less so, because I > am in a bad mood. > > $8 for a medical device? If the raw parts cost just $1, the device > will HAVE to sell for at > least $25 just to cover the cost of insurance. So now you will need to > include another > $15 MORE of parts to cover the need of an insurance company to feel > safe in covering an > $8 device (few will). > > Medical items cost a LOT of money because innovation is NOT what > drives that industry. > What drives it is INSURANCE. If you are unable to convince an > insurance company that > it works PERFECTLY, they won't cover it, and you are sunk. Examples: > PIC's 10-bit A/D > won't cut it, but the 18-bit MCP3421 WILL cut it, but that triples the > cost. > > Did you know that there are few electronic parts that are even ALLOWED > to be designed into a medical product? National Semiconductor makes > wonderful parts, but National will > NOT sell parts to you if they will be used in a medical device; and > believe me, they ALWAYS find out. The people that WILL sell you parts > will sell you the expensive, super-tested version, not the cheapy > 50-cent one. And the list goes on and on. > > I have designed a couple of very simple medical devices in years past, > and frankly, I'd > never do it again. > > --Bob A > > On Mon, Feb 16, 2009 at 10:16 PM, Benjamin Grant wrote: > > Hi all > > Sorry if you felt that my schematic was insulting. I will rework it soon > and > > fix my errors as well as replacing the LEDs with an LCD display. I have > > worked on the schematic a little bit - cleaning up wires and labeling > parts > > Solarwind, all those methods are possible, but reflection/absorption > > techniques are the most straightforward, reliable techniques. Again > Olin, > > this is not my area of expertise and I will try to get my schematic more > up > > to par with your standards, but your argument that I'm trying to use "a > > bunch of chumps for free advice" fails in this instance, as I'm a chump > > voluntarily spending a large amount of time trying tot develop a > nonprofit > > product. Please, if in anyway you think I am using you to help those in > > need, feel free to filter any messages from me, I will not be the least > bit > > offended. I will, however, relabel my parts and straighten my lines. > > Admittedly, not assigning new names to parts was a very poor mistake, and > > I'm sorry I overlooked it. I am looking at using the PIC16F723 because it > > meets the nanotechnology specs recommended by others and the lumex > > LCD-S301C31TR 3 digit LCD display. While the lumex datasheet says it > > requires 5 V, other sources show that it can be used at 3 V with slightly > > lower contrast, so I believe running the PIC at 3 V will be feasible. It > > has 24 pins but 2 are unnecessary(decimal points) so that leaves me with > 3 > > I/O pins from the pic for controlling the LED and receiving the input. > The > > schematic found here > > < > http://web.archive.org/web/20080103013653/http://focus.ti.com/docs/solution/folders/print/330.html > >is > > what I'm basing the key components of my circuit off of. It recommends <1 > pF > > feedback capacitance and has a similar set up for the photodiode as me, > > however, posters here have criticized both of these in my schematic. So > I'm > > wondering if the reason that TIs schematic is fundamentally sound while > mine > > is not is because they utilized an auto-zero op amp with exceptionally > low > > voltage offset. Olin pointed out that any DC offset is going to be > > integrated and will result in a signal that is not what I would expect. > > Furthermore, he pointed out(correctly) that I had a NPNs in my schematic > > where a PNPs belonged. I've since fixed that. My cleaner schematic is > shown > > here in bmp > > >or > > emf . I > > will have my next revision in PDF format. Hopefully this schematic is > easier > > to read than my previous one. If anyone has suggestions as to why the TI > app > > note is suitable in their case but not mine and any circuit specific > advice, > > I'd greatly appreciate it. Thanks a lot > > -- > > http://www.piclist.com PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist