Terminal boards for WebControl

[rossw]

can we get an unassembled kit here in the US? I'm looking to use it just as a breakout (not use the opamp).

Absolutely.... do you want just the bare board?? Are you wanting the A/D inputs as well, or just the digital inputs?
To use it as a digital input only breakout board needs just the 16-pin header and the screw terminals. Analog without the opamp needs some jumpers as well, but that's trivial and I can show you where to put them. Bare boards $5 AUD each + $2.35 postage

 

[mminehan]

Ross, I'd like to buy 5 long kits from you. I'm new to the board and don't seem to be able to send PMs. I think it's a number of posts thing. I'm a kiwi by the way. I'll try looking for the pm thing again.

 

[rossw]

Ross, I'd like to buy 5 long kits from you. I'm new to the board and don't seem to be able to send PMs. I think it's a number of posts thing. I'm a kiwi by the way. I'll try looking for the pm thing again.

I tried to send you a message and when I hit send, it says "The member mminehan can not use the messaging system"
Grr!

How about you shoot me an email - " rossw at rossw dot net " should get to me fine.

Happy to send you 5 long kits by whichever works out to be the most economical means. What gain would you like them set to? Or should I just send you some resistors and let you source them locally to suit your needs?

 

[mantamania]

Hi Ross !

Yesterday I got mail.
Normaly its bills and ads, but this time it was a letter from Australia with
two cute boards !
In the matter of days from a hot Australia to a icecold Sweden, that's impressiv.

Thank you wery much ray:

/S

 

[rossw]

Hi Ross !
Yesterday I got mail.

Hooray! Now that you have them, I'm sure you'll have questions - please don't hesitate to ask. I'll assist however I can.

 

[mminehan]

Ross, thanks so much for your development of this board. It opens up a whole host applications for the webcontrol interface.

One thing I have been trying to figure out is how to use them as pH and ORP meters. For pools and aquariums.
pH probes are high impedance low voltage probes. The problem is they produce both +ve and -ve voltages depending on the pH (http://www.66pacific.com/ph/simplest_ph.aspx and http://www.ti.com/lit/ds/symlink/lmc6001.pdf)

Is there and easy way to modify the circuit to allow the connection of a pH probe (i.e. convert a range that includes -ve and +ve milivolatges to 0-10V)?

This would be useful for many cocooners I'm sure.

Marty

 

[mminehan]

Actually, I should have read around a bit more. The second link has a very good exmple of a pH meter circuit with offset to adjust the output of the probe from 0 to 1440mV. This output could then be fed into the opamp of your board to give a range of 0 to 10v. A quick formula in whatever software is reading the board (1.4pH per V) would give you the pH of your pool in you automation software (Homeseer in my case).

M

 

[rossw]

Ross, thanks so much for your development of this board. It opens up a whole host applications for the webcontrol interface.

One thing I have been trying to figure out is how to use them as pH and ORP meters. For pools and aquariums.
pH probes are high impedance low voltage probes. The problem is they produce both +ve and -ve voltages depending on the pH (http://www.66pacific...implest_ph.aspx and http://www.ti.com/li...ink/lmc6001.pdf)

Is there and easy way to modify the circuit to allow the connection of a pH probe (i.e. convert a range that includes -ve and +ve milivolatges to 0-10V)?

This would be useful for many cocooners I'm sure.

Marty, the opamp configuration I've provided on the board is quite flexible, and provides for offset operation fairly easily.
There is a small prototyping area on the board where you can put some resistors for biasing networks. There is also one opamp left in the package you could bias up for a low impeadance reference.
I will have a look at the circuit you indicate to see if it's "easy" to achive without an extra amplifier.

Hmm, I think the drive of the pH probe will be just too low. While providing gain and offset in one hit is managable, doing so with the tens-of-megohms input impedance required is going to be far too much to ask of such an inexpensive opamp. A buffer in front will make a lot of difference!

 

[mminehan]

Ross, thanks for looking into this. I seems as you say using an external circuit infront of the opamps is the way to go.

I'll email you with my order.

Thanks M

 

[swaggy]

Ross

Just sent you PM, hoping to get two of the long boards.

Regards
Yuri

 

[rossw]

Sorry everyone - the last of these boards are now gone.
I will be getting some more made, but they'll be slightly different - more details soon.

 

[ChubRock1]

Hey Rossw
 
I would be interested in a couple assembled kits as well to the US.  Let me know when the new ones come in.

 

[swaggy]

Sorry everyone - the last of these boards are now gone.
I will be getting some more made, but they'll be slightly different - more details soon.

 
Curious - what improvements will the new board have?

 

[rossw]

Curious - what improvements will the new board have?

 
Haven't nailed it down yet, but I plan to address all of the limitations I encountered with the first version.
For example, the first version was intentionally made using fixed resistors. Less board space, cheaper, lower noise, less drift. However the big limitation with that has been trying to tweek gains to exactly align full scale input with webcontrol A/D full scale. The new board will use 20-turn trimpots for the gain.
 
While using one of the boards with a 3-axis accelerometer, I would have liked a power supply +V available at the analog input connector, so that's going in too. (5 pins instead of 4).
 
Installing resistors and a jumper in either of two places to set inverting or non-inverting operation was ok, but if I replace the resistors with trimpot, setting the mode would require jumpers either way. I'm putting pads to set the mode, but also putting tracks between the pins for the most common configuration (non-inverting).
 
Things like that will make little difference to most people, but tidies it up a bit in other regards, and makes assembly quicker. The total cost will be more though, because the 20-turn trimpots are more expensive than fixed resistors, etc.
 
Oh, and to keep the board the same size I've had to go to a SOIC (surface mount) amplifier. Makes it harder for the average DIY to assemble, but I can always solder the chip here before shipping.

 

[CAI_Support]

When will be next batch ready, Ross?