CAI_Support
Senior Member
Really nice board!
Terminal boards for WebControl
- Thread starter rossw
- Start date
Thankyou!
Here's one assembled up with 3 channels to convert 0-75mV (typical current shunt) to 0-10V
Observe the jumpers - this is configured as 3 x inverting amplifiers, as my shunts measure charging current.
For non-inverting, the resistor is installed in the other (diagonal) position, and the jumper in the alternate position.
I also have a limited number of stand-alone, 4-channel amplifier boards.
Pictured here (obviously) without gain resistors. Basically, it's 4 channels in, 4 channels out, plus ground and supply in and out.
First in, best dressed.... unless there's enormous demand for them, once these are gone, that's it. (Send me email, or ask here if you want any)
Pictured here (obviously) without gain resistors. Basically, it's 4 channels in, 4 channels out, plus ground and supply in and out.
First in, best dressed.... unless there's enormous demand for them, once these are gone, that's it. (Send me email, or ask here if you want any)
CAI_Support
Senior Member
I think a lot of people want to know how to buy them from you 
I've done the costings on the boards, paypal charges etc, based on what I actually paid for everything.
The weight of an assembled board is just on 20 grams, so easily fits in the lowest weight category.
I've researched what I can post, and the maximum thickness for an airmail letter is 20mm, and an assembled board is exactly 20mm, which leaves nothing at all for padding. International airmail for under 50g (and under 20mm thick) is $2.35 (plus the envelope/padding), which jumps to a minimum $17.20 for a "small parcel under 50g" but over 20mm thick! I don't think I'll be sending many assembled and tested kits. (I have a friend in the USA who is prepared to drop-ship them - I can send a bunch of assembled boards to him and he will re-post them domestically, if there is demand).
Prices in AUD, paid using paypal, postage additional. I can fit two kits or up to 6 bare boards in one letter.
Bare board: $5.00
Short kit: $9.00
Long kit: $12.00
Visit http://auspost.com.au/apps/international-letter.html to check the actual postage to your part of the world.
Select your country, select "Up to 50g". On the next page, select your preferred method (Airmail, registered etc, your choice)
The weight of an assembled board is just on 20 grams, so easily fits in the lowest weight category.
I've researched what I can post, and the maximum thickness for an airmail letter is 20mm, and an assembled board is exactly 20mm, which leaves nothing at all for padding. International airmail for under 50g (and under 20mm thick) is $2.35 (plus the envelope/padding), which jumps to a minimum $17.20 for a "small parcel under 50g" but over 20mm thick! I don't think I'll be sending many assembled and tested kits. (I have a friend in the USA who is prepared to drop-ship them - I can send a bunch of assembled boards to him and he will re-post them domestically, if there is demand).
Prices in AUD, paid using paypal, postage additional. I can fit two kits or up to 6 bare boards in one letter.
Bare board: $5.00
Short kit: $9.00
Long kit: $12.00
Visit http://auspost.com.au/apps/international-letter.html to check the actual postage to your part of the world.
Select your country, select "Up to 50g". On the next page, select your preferred method (Airmail, registered etc, your choice)
If by that you mean you don't need the amplifier, I'll show you which pins to put wire links between to completely bypass the amp. Then the digital inputs will go directly to their screw connectors, and the analog inputs will go directly to theirs with nothing in between.
mantamania
Member
[sub]Hi rossw ![/sub]
[sub]I want to buy 2 long kits, can you PM me the total cost incl. shipping[/sub]
[sub]to Sweden, and the PayPal adress where I will pay.[/sub]
[sub]A simple shematics and a "how to calculate amplifiing" would be nice.[/sub]
[sub]A Happy New Year ![/sub]
[sub]I want to buy 2 long kits, can you PM me the total cost incl. shipping[/sub]
[sub]to Sweden, and the PayPal adress where I will pay.[/sub]
[sub]A simple shematics and a "how to calculate amplifiing" would be nice.[/sub]
[sub]A Happy New Year ![/sub]
Mantamania, calculating gain is actually fairly straightforward.
Firstly, identify what your input voltage range will be. Example, 0-1V
Secondly, work out what voltage range you want to offer to the WC A/D input. For maximum useful range, you want 0-10V
The gain you require is (in this case) +10 (10-0) / (1-0) = 10/1 = 10.
If you want a non-inverting amplifier (as in this case), per the notes on my schematic:
In this configuration, the gain is simply 1+(R1/R3)
So we want R1/R3 to be 9. I like to use "middle-of-the-road" resistors, not so high noise is a problem, and not so low current is a problem.
Using standard resistor values, 30K for R1 and 3K3 for R2 gives a gain of 1+(9.0909) = 10.09.
This is probably "close enough" for the majority of cases. (Adding a 33R in series with the 3K3 would make the gain 10.0009)
The only remaining problem is that as the terminal board is intended to run off the WC boards internal 5V supply, it will never reach the 10V output and will clip. I considered this in the design, and it's fairly simple to cut one track and run the board from another supply - in my case, I am running the webcontrol board from a 12V regulated supply, so I simply use that.
Here's a photo showing the mod:
Making the mod is fairly easy. Take a sharp knife (razor blade, scalpel etc), cut across the track about 2mm wide. Place a hot soldering iron on the cut section, allow it to get hot. While gently pressing down onto the track with the iron, slide the iron and track out cleanly. You will feel when it "lets go". Of course, you can use a dremel if you prefer, but this method is quick, clean and easy.
Firstly, identify what your input voltage range will be. Example, 0-1V
Secondly, work out what voltage range you want to offer to the WC A/D input. For maximum useful range, you want 0-10V
The gain you require is (in this case) +10 (10-0) / (1-0) = 10/1 = 10.
If you want a non-inverting amplifier (as in this case), per the notes on my schematic:
In this configuration, the gain is simply 1+(R1/R3)
So we want R1/R3 to be 9. I like to use "middle-of-the-road" resistors, not so high noise is a problem, and not so low current is a problem.
Using standard resistor values, 30K for R1 and 3K3 for R2 gives a gain of 1+(9.0909) = 10.09.
This is probably "close enough" for the majority of cases. (Adding a 33R in series with the 3K3 would make the gain 10.0009)
The only remaining problem is that as the terminal board is intended to run off the WC boards internal 5V supply, it will never reach the 10V output and will clip. I considered this in the design, and it's fairly simple to cut one track and run the board from another supply - in my case, I am running the webcontrol board from a 12V regulated supply, so I simply use that.
Here's a photo showing the mod:
Making the mod is fairly easy. Take a sharp knife (razor blade, scalpel etc), cut across the track about 2mm wide. Place a hot soldering iron on the cut section, allow it to get hot. While gently pressing down onto the track with the iron, slide the iron and track out cleanly. You will feel when it "lets go". Of course, you can use a dremel if you prefer, but this method is quick, clean and easy.
Because the LM2902 isn't rail-to-rail, it will only get to about 3.7V maximum on a 5V supply, so would need even lower resistor than 62K
The idea is sound - it was my second choice though, as modifying my terminal board (and not the webcontrol board) means I can swap WC boards without modification to them (as I'm about to do, because the board I have in service simply doesn't support the second ADC!)
CAI_Support
Senior Member
Ross,
With your terminal board, users can do a lot more things with analog inputs!
With your terminal board, users can do a lot more things with analog inputs!
potts.mike
Active Member
Rossw,
I am going to want two of the long kits. Shipping to 80222 in the US. Send me a PM with total cost and the details.
-Mike
I am going to want two of the long kits. Shipping to 80222 in the US. Send me a PM with total cost and the details.
-Mike
