Questions about Aux input plugs on webcontrol8 vs 32

TJF1960

Active Member
I am considering replacing a webcontrol8 board with a new beta 32 board. I have been looking at the pin outs of the Aux input connector and noticed the pin reference. numbering system is different between the 2 boards.
 
webcontrol 8 pinout is such:
8  7   6   5   4   3   2   1
9 10 11 12 13 14 15 16
 
whereas webcontrol 32 is such:
 
39 37 35 33 31 .......
40 38 36 34 32 .......
 
Is that correct?
 
I was hoping I would be able to plug the Aux input plug from the wc8 board onto the wc32 board but it looks like all the pins were re-ordered so, I am looking for ideas on how would be the quickest way (in terms of down time) to make the board swap. Perhaps a 16 to 40 adapter?
 
Thanks,
Tim
 
The pin layout from WC32 and WC8 are totally different, because there are a lot more TTL input/output and analog input.  To reduce noise, we have to put analog inputs together on the header.
 
Ross is planning an IO board for the WC32.  Since Ross already made IO board for WC8, he has a lot experience on that.  Maybe he could make a bear board for anyone who don't need all IO connections to only populate some connectors.
 
There will be a change from beta board to release board.  That is the USB connection from mini USB to four pin header, so that IO board can extend that to a full size USB connector. 
 
I think I am going to go ahead and make a small pcb with a 16 and 40 pin header so I can just remove the wc8 and install the wc32 and plug the existing 16 pin connector on the interface board then the 40 pin from the interface board to the wc32. So as long as there are no changes to the Aux input header on the release board I will be good to go.
 
One other question. I had an older hardware rev board, before the current hardware version and when I replaced it with the current hardware rev board I noticed a reading difference of the AIP's probably due to some resistor changes between the boards. Will I experience anything similar going from the current hardware rev wc8 to the beta wc32 (or for that matter the final release wc32)?
 
Thanks for your great questions. AUX pin out will not change.
 
WC32 full scale is 5V instead of WC's 10V, that will make IO board with amp easier.  It will not change that.  The beta WC32 board has high impedance for the AIP inputs, similar to the WC8 board. In the release version WC32 board, AIP input impedance will be reduced from 100K to 5K.  They will still same 5V full scale, but require more current to drive the AIP input.  The reason for that is the AIP accuracy will be higher with lower input impedance per Microchip spec.  If the 5K input impedance is too low for your application, it will need to have an IO board with amp to make up the current requirement.
 
CAI_Support said:
WC32 full scale is 5V instead of WC's 10V, that will make IO board with amp easier.  It will not change that.  The beta WC32 board has high impedance for the AIP inputs, similar to the WC8 board. In the release version WC32 board, AIP input impedance will be reduced from 100K to 5K.  They will still same 5V full scale, but require more current to drive the AIP input.  The reason for that is the AIP accuracy will be higher with lower input impedance per Microchip spec.  If the 5K input impedance is too low for your application, it will need to have an IO board with amp to make up the current requirement.
 
Just a quick question: 0-5V is reasonable, but I think it should be 5.12V FSD (which makes it a neat 5mV/bit).
Alternatively, 0-3.3V (which I believe is the native scale for the ADC inputs anyway). The advantage with that is that I can run a normal, inexpensive opamp for input conditioning off 0-5V and still be able to achieve full scale, whereas with 0-5V input it needs a more expensive rail-to-rail chip.
 
While I have peoples attention, I've been trying to figure out if the best option is to use optoisolators for all inputs or just some. If people want them powered remotely or locally, or the option of either etc.
 
Another consideration is that with there now being 8 outputs on the aux connector, if I should put either relays or open-drain FETs on the board?
 
To CAI: have you considered (or would you consider) changing the 40 pin connector for a 50 pin, and replicate the 8 TTL outputs onto the internal connector?
Why? Well, exactly as questioned above - changing boards out will be a lot easier if you don't have to undo the connectors each time.
 
To everyone: because there are now so many connections to bring out, I'm not sure that a "piggyback" board is practical any more, and I'm thinking that the "terminal and amplifier" board for the WC32 might need a complete rethink. I'm currently in favor of making it larger than the WC32 as a "baseboard" that the WC will plug into, rather than the other way around. (The alternative (and its not a mutually exclusive design consideration) is a ribbon-cable between the two))
 
Thoughts?
 
Hi Ross,
 
Great insite. my 2 cents:
 
Agree with the first paragraph.
 
"While I have peoples attention, I've been trying to figure out if the best option is to use optoisolators for all inputs or just some. If people want them powered remotely or locally, or the option of either etc"
I suppose you could create a spot for the opto's on all inputs, if they all or some are not needed they can be jumpered to bypass.
 
"Another consideration is that with there now being 8 outputs on the aux connector, if I should put either relays or open-drain FETs on the board?"
Same with above in regards to FET's. If relays are to be used they (board and all) can be had on eBay pretty cheap.
 
I also agree with the 50-pin instead of the 40-pin if there is room.
 
"To everyone: because there are now so many connections to bring out, I'm not sure that a "piggyback" board is practical any more, and I'm thinking that the "terminal and amplifier" board for the WC32 might need a complete rethink. I'm currently in favor of making it larger than the WC32 as a "baseboard" that the WC will plug into, rather than the other way around. (The alternative (and its not a mutually exclusive design consideration) is a ribbon-cable between the two))"
This too is more or less what I had in mind, a "baseboard" which is larger than the wc32, which it would just about have to be to allow for all the different connections and additional circuits.
 
Thanks,
Tim
 
 
 
 
There is no place to put a larger connector on it. Our idea is that for people who already have WC8, the WC32 layout is similar, if they replace the WC8 board with WC32 board, it will have same 8 TTL output, and fit in the same metal chassis.
 
The AIP input is divided by a 5K and a 10K resistors, so that its AC impedance is about 5K, and DC resistance is 15K. The result is like 4.99V full scale.  That is already fixed on the manufacture board.  Op Amp can use adjustable pot to decide whatever the full scale range.  For most people want to use op amp is to measure much smaller signals, by adjust how much amplification would be, it is easy to make the full scale in any range.  Am I correct?
 
CAI_Support said:
There is no place to put a larger connector on it. Our idea is that for people who already have WC8, the WC32 layout is similar, if they replace the WC8 board with WC32 board, it will have same 8 TTL output, and fit in the same metal chassis.
 
The AIP input is divided by a 5K and a 10K resistors, so that its AC impedance is about 5K, and DC resistance is 15K. The result is like 4.99V full scale.  That is already fixed on the manufacture board.  Op Amp can use adjustable pot to decide whatever the full scale range.  For most people want to use op amp is to measure much smaller signals, by adjust how much amplification would be, it is easy to make the full scale in any range.  Am I correct?
 
Understand (and appreciate) the benefits in maintaining the same formfactor. To fit a 50 pin connector would require moving the voltage regulator. There looks to be enough room to do it - just. Was just a suggestion though. (And I wasn't suggesting dropping the 8 output connector, but DUPLICATING them on the 50-way aux connector so we could access all 16 outputs that way (as well as the bottom 8 outputs via screw terminals)
 
As for the 5K/10K divider, yes, we can amplify smaller signals (or attenuate larger ones) to this span using gain control on the amplifier. The difference is that in order to get to 5V from the opamp requires either:
 ( a ) MORE than 5V supply (at least 6.5V)
or
 ( b ) more expensive rail-to-rail opamps.
 
If you provided access direct to the input pin, you could:
 ( a ) save 10K and 5K resistors on each channel
 ( b ) drive opamp output directly to ADC inputs for even lower source impeadance
 ( c ) still use inexpensive opamps powered directly off 5V rail
 ( d) provide overvoltage protection by a small diode from ADC input direct to +3V3 supply
 
(I'm assuming the chip will survive at least one diode drop above Vcc on ADC inputs?)
 
WC32 production board will no longer use regulator, rather use DC-DC inverter, allowing using wider range of power supply, better efficiency, in addition to provide more power in 5V for supporting USB LCD keypad/display.  The space where regulator is currently on beta board will be a lot of other components for this DC-DC inverter function.
 
CAI_Support said:
WC32 production board will no longer use regulator, rather use DC-DC inverter, allowing using wider range of power supply, better efficiency, in addition to provide more power in 5V for supporting USB LCD keypad/display.  The space where regulator is currently on beta board will be a lot of other components for this DC-DC inverter function.
 
OK, that's a good use of the available space too :)
What safe input range are you expecting it will work over? Presumably a buck only, so 6V to what... 30+ ??
 
We noticed the WC32 board hardware spec sheet IO pin labeled wrong.  Here is the correct one.
 

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CAI_Support said:
We noticed the WC32 board hardware spec sheet IO pin labeled wrong.  Here is the correct one.
 
Some thoughts....
 
1. You have labeled pins 6 & 8 on J4 as being "+5V (out)". Is it still feasable to feed +5V *TO* the WC board via this pin? Is the DC-DC converter happy to have 5V applied to its output with nothing on the input?
 
2. J1 still says "+7V - +9V input" - if the DC-DC converter is good for 24V, it would be nice if this indicated perhaps +7 - +18 or +20V input.
 
3. J3 says pin 3 is +3.3V out. Is it REALLY +3.3? I had major problems with my DS18B20 sensor arrays on 3.3V on the WC8 boards and used to cut the track and feed them with 5V. In later revision boards you did the same. I hope this is just a documentation error!
 
4. How about some physical dimensions? Board size, hole spacings etc. I'd (personally) also like to know the spacing between connectors so I can hopefully get back to making this baseboard!
 
Hi   Ross,
 
Production board J1 input can be from 4.75A to 24V. If you have 5V power, it will work, too.  But absolute maximum input is 26V.  If someone feed unregulated 24V, it could have spike kill the inverter.  We don't recommend to push to the limit on that one.  We may change the spec to 5V to 12V, so that most popular power supply will work.  This documentation is about the sample board, which is still 7-9V.
 
Thanks for pointing out J3 is actually 5V. 
 
You have the board there already.  The size is the same for production and the beta board.  40 pin connector did not move.
 
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