Help with RDAS Compact Expansion Port

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patelldp

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I need some help with monitoring a transducer with an RDAS Compact. The transducer is a 0-2500psi Statham unit with 28V excitation that has been proven using my Dataq DI-145. I reconfirmed today that the transducer is working appropriately with my Dataq...0V when open, then 3.75V when the test leads are connected (75% of full 5V) as expected.

The issue arises when I attach to my RDAS. The RDAS has a serial port, but I decided to simplify by connecting to the RDAS with simple jumpers. I attached the positive output from the transducer to the #7 pin (red jumper), and the negative output from the transducer to the #13 pin (brown lead).

RDAS Wiring.jpg

After all physical connections were made, I did the following:

1. Stood RDAS vertical
2. Powered RDAS with 9V, allowed to boot
3. Powered the transducer
4. Shorted the test leads on the transducer (per above, should report 3.75V)
5. Flipped RDAS upside down, then twisted the unit in order to trigger the g-switch
6. Allowed unit to sit for a bit after detecting launch while moving it a bit
7. Powered down RDAS, removed connections, then hooked up to computer and downloaded the "flight data"

Within the flight data (which appeared normal, but it's here), the ADC 0-5 selection buttons at the top of the window are grayed out, meaning no data collected. It's my understanding that there should be evidence of when I shorted the test leads and a steady 3.75V throughout the duration of the "flight."

TL;DR: Transducer works with Dataq, RDAS does not record. May be issue with connection to RDAS serial expansion port?

Help!
 
If you want the RDAS to record data from the analog inputs you must tell it too first. The configuration menu is the place for that.
 
If you want the RDAS to record data from the analog inputs you must tell it too first. The configuration menu is the place for that.

Would you look at that...let's try that...
 
That doesn't appear to result in the anticipated output. I toggled on ADC0 and ADC1 (1 as a control as nothing is hooked to it) and ran the same tests except for manually toggling the transducer's test leads to try to show an alternating between 0 and 3.75V. Instead, I got a bunch of garbage voltage readings that toggle between 0.3 and 4.5V, seemingly random, and very similar between the 2 channels.

File here.

Next test will be with all of the ADC channels toggled on to see if my pin number identification skills are wonky...
 
Is my pin numbering correct? Is the red wire on pin 7 and brown on pin 13?
 
Is my pin numbering correct? Is the red wire on pin 7 and brown on pin 13?

I have no idea as it depends on the ribbon cable and the connector. But if it is standard rainbow ribbon cable with brown on pin 1, then no.
 
I have no idea as it depends on the ribbon cable and the connector. But if it is standard rainbow ribbon cable with brown on pin 1, then no.

I broke apart a ribbon cable. These are just 2 independent wires acting as jumpers. If you look at my first post you'll see exactly what I did.

+ OUT from Transducer to Pin 7 (ADC0)
- OUT from Transducer to Pin 13 (GND)
 
Instead, I got a bunch of garbage voltage readings that toggle between 0.3 and 4.5V, seemingly random, and very similar between the 2 channels.
The acceleration and pressure data is also wonky so you have some other problem.

Your connections are correct.
 
The acceleration and pressure data is also wonky so you have some other problem.

Your connections are correct.

When you say "wonky," would you mean that it doesn't represent a standard flight? If that's the case, it wasn't a standard flight, it was a bench test of me whipping the unit around like crazy trying to trigger the g-switch.

Your post also made me a little concerned that the unit may be damaged, so I flipped it over and took a look. It appears these units use some sort of diode and one of them may be damaged. It's located near the RS-232 connector and I did my best to take a macro shot of it. If it is broken and it bricks the unit, man I'll be pissed. That would make the second damaged RDAS I will have acquired.

IMG_3505.jpg

IMG_3502.jpg

IMG_3503.jpg

Here's what a seemingly intact one looks like:
IMG_3504.jpg
 
Last edited:
When you say "wonky," would you mean that it doesn't represent a standard flight? If that's the case, it wasn't a standard flight, it was a bench test of me whipping the unit around like crazy trying to trigger the g-switch.
Wonky: +50G/-65G and +/-17,000ft. It looks a lot like the analog data and nothing like the first data set.

Instead of flailing around trying to trigger the G-switch algorithm, configure the altimeter to use a breakwire for bench testing.
 
I've used an RDAS as a test stand data logger many times. Just start the logging using a break wire configuration. I have a relay as the breakwire. The relay coil is actuated with the igniter leads.

Once you have the data exported from the RDAS, try my "Thrust Curve Tool" program to plot the results and create an ENG file to use in simulations.
 
I've used an RDAS as a test stand data logger many times. Just start the logging using a break wire configuration. I have a relay as the breakwire. The relay coil is actuated with the igniter leads.

Once you have the data exported from the RDAS, try my "Thrust Curve Tool" program to plot the results and create an ENG file to use in simulations.

John,

Sounds like you have direct experience with this, then. How did your set up compare to mine? As stated, my transducer outputs 0-5V to two leads. I put the positive out lead to pin 7, negative out lead to pin 13. That should result in data collection on ADC0.

I'm having my RDAS diode repaired. We'll see if that changes anything.
 
I have flown a three axis magnetometer so I have some experience using the RDAS Compact expansion port if that matters to you.

It does if you'll share how you hooked it up :)

Was the magnetometer powered by its own battery? Did you have a positive and negative signal wire pair going to the RDAS? What pins did you hook it up to?
 
It does if you'll share how you hooked it up :)

Was the magnetometer powered by its own battery? Did you have a positive and negative signal wire pair going to the RDAS? What pins did you hook it up to?

It got its power from the RDAS expansion port so it shared a ground with the RDAS. The HMC2003 had its own signal conditioning with 0-5V outputs so I just connected the signals to the obvious ADC input pins (7 etc.). Three magnetometer channels and the 2.5V reference voltage were recorded and the data files are linked at the bottom of that page in case you want to have a look.

I switched to using the Ultralife 9V Lithium batteries because battery life was poor at the best of times and I increased the load.
 
Same set up as before, now with a breakwire configuration to save from dislocating any arm parts.

It appears there's an issue with the RDAS's expansion port. I have the diodes on order and will have the unit repaired. If that doesn't work, this will get relegated to dual deployment functions after a test flight or two. I also plan to trip the unit and check the barometric sensor with my propellant vacuum system.

https://drive.google.com/file/d/0B_F71R0pfXLOenNCaE8yTjliSzA/view?usp=sharing
 
It is almost certainly not a problem with the expansion port. I don't know what you don't like about the recorded data.
 
John,

Sounds like you have direct experience with this, then. How did your set up compare to mine? As stated, my transducer outputs 0-5V to two leads. I put the positive out lead to pin 7, negative out lead to pin 13. That should result in data collection on ADC0.

I'm having my RDAS diode repaired. We'll see if that changes anything.

I will have to take apart the test stand box to see how I wired the expansion port. Originally built 15 years ago and my memory isn't what it used to be. ;)
 
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