Hi Paul, no I waited for several send/returns before doing the test.
Also just fyi when all ABCD unjumpered and I send VA VD I get the expected 255 and 255 but when I jumper D, instead of getting A A as 255 and D as 0 - both A and D return 0 and 0
Wayne
Note: I do not always get exactly 255, it varies around 252 and 253
Paul
I now have both pressure sensors working on the ssc32, really works well. I am limited to just 2 3-wire fsr’s so I have placed a question in the abb forum for help in what next to buy to run more sensors.
Thanks
Are you sure the jumpers are going to 5vdc and or ground? If you jumper all of the inputs then you should see the following…
A = 255
B = 0
C = 255
D = 0
Because the terminals are laid out like this.
[A] +]
** [G]
[C] +]
[D] [G]
The 255’s will fluxuate a little as it’s measuring the 5vdc line. It may be 4.97 so it may read 253 etc.**
With four analog inputs on the ssc-32, I would think you could easily run four sensors. If more sensors are needed, then a simple multiplexing setup might be used to monitor a lot of sensors connected to one analog input.
The ultimate connecton scheme would have been to duplicate the three row setup the Bot Board uses. However there was just not enough room to do this on the SSC-32. So you just have to do a little wiring to get what you want. Have two sensors use one pair of +/- connections. You can use servo wire extenders as a jump start to making the connectors you need.
I’d use one + (or VCC) to supply all four sensors, one - (or common ground) to connect to all four sensors, and then connect the sensor individual outputs to the A, B, C, and D analog input pins. This is based on what I see on the ssc-32 schematic diagram.
This is exactly what I have in mind to do to make my Renesas starter kit board into a robot controller. I’ve ordered several of the single ended servo cables to start this off with and am working on a way to make the board I/O pin connectors into 3 wire setups for sensors and servos.
If you are going to use the ABB, you need the MCU on the ABB to handle the sensor data, or create a serial program that will comunicate from your PC to the ABB then to the SSC-32. Either way, you will need an MCU.
If you can live with a ~.7v loss to the analog input, then you could supply the + to the 8 sensors from the 8 available servo pins. You would use these pins in the byte mode so each could individually be set high at +5v to supply the desired sensor. Between each sensor output to the analog input pin, you would use a diode to prevent back feeding thru the other sensors. A cheap signal diode from Radio Shack has a .7v voltage drop across it, so you would only be able to measure from 0 to ~4.3v, which may or may not be an issue for what you want to do. You can get ~.1v voltage drop diodes, but not at RS. You connect the output of all the diodes to a single analog input pin. When you want to measure the pressure on a sensor, you set the associated servo pin high (with the others set low), and then read the analog input pin to get a pressure value from the sensor.
Unfortunately I am not a hardware guy so this procedure with the diode while easy for you and others with electronics experience, is very intimidating and probably beyond me at this point. Perhaps 3-4 months down the road, I could attempt this.
As to doubling up the fsr’s, I was able to attach 4 pressure sensors to the ssc and they worked great.
I am now reading up on the ABB for additional sensors.
Hi zoomcat
Ok you have convinced me, I will see about getting diodes this week and give it a try. In retrospect this would really make the ssc32 quite flexible.
A couple questions if I may:
What serial command do I send the servo to query it ?
For the pressure fsr is the diode before or after the resistor in the wire going to the analog input pin ?
So if I understand this for eight of the 3-wire fsr’s…
Supply the + to the 8 sensors from the 8 servo pins.
The - to the 8 sensors from the 8 servo pins
Connect the output of all the diodes to a single analog input such as A
Powering up and down sensors is not really a good idea as many sensors require several milliseconds to startup and even then the first read value is usually to be thrown away.
ZC is on the right track though. use the port to control a multiplex analogue switch. A 4 to 1 analogue switch would only require the use of 2 bits of a port. The sensors could be powered on continuously and switched and read as required via the analogue switch.
Theoretically, you could run up to 256 different sensors from one eight bit port and one analogue input. Not so good in practice but do-able.
