• Scam Alert. Members are reminded to NOT send money to buy anything. Don't buy things remote and have it shipped - go get it yourself, pay in person, and take your equipment with you. Scammers have burned people on this forum. Urgency, secrecy, excuses, selling for friend, newish members, FUD, are RED FLAGS. A video conference call is not adequate assurance. Face to face interactions are required. Please report suspicions to the forum admins. Stay Safe - anyone can get scammed.

JCDammeyer's 42 projects

My 2c...

I don't have a lot of faith in much of the Adafruit/Arduino type circuits, certainly some marginal design that is great for beta but not much beyond that.

How about slowing that SPI bus way down (temporarily), decent chance it will start behaving.
or
Try Susquatch's suggestion of the pull downs (might work but sounds a bit iffy)
or
As ugly as the kludge will be use 74LVC1G17's to do a proper conversion. If it works you know that was the problem if it doesn't than perhaps there is a software bug.
 
@slow-poke I had slowed it down already. Way slow. My scope can actually decode SPI signals. I make the yellow probe the /CS, Blue the SPI_CLOCK and Green the MasterInSlaveOut pin. The scope then detects the SPI message and shows the decoded hex. It shows zero when there's no output which is what was happening. Once it was producing good numbers the LED display started reporting the correct information.

I changed to using the same 74HC138 used for the LED displays instead of a line direct from the processor. No software change required. While doing that one of the jumper wires I used to make connections from the DB-9 to the header fell off.

Hmmm... Turns out that was the one used to select the TC chip. Maybe this was always just a loose connection?

Anyway. Now that I'm using a 74HC138 active low select it works perfectly. No software change required here because of the way I did the addressing. Of course after my last modification it worked on the bench too but was a bit erratic on the compressor.

We'll see. Before I put it back in the shop I'll try speeding up the SPI again to see if it breaks.
 
Yahoo! Put the SPI clock speed back up to 1 MHz. I think I can make the delay before and after the clock a lot shorter again too.

1720407835858.png

There we go. Takes about 37uSec to acquire both the Thermocouple temperature and Cold Junction Temperature. Hasn't had any false readings.

1720408930892.webp
 
Last edited:
Great, glad you sorted it out.

Tek scope?

The built-in protocol decodes sure are handy. I only have a 4 channel scope at home would like a MSO, but can't really justify it for home use.
 
slow-poke said:
Great, glad you sorted it out.

Tek scope?

The built-in protocol decodes sure are handy. I only have a 4 channel scope at home would like a MSO, but can't really justify it for home use.
Click to expand...
Yes. It does I2C, SPI, CAN bus. I couldn't justify the $1600 US price for the RS232 UART module. Instead I bought the Digilent Analog Discoverly scope kit that did that and does CAN, SPI, I2C and it was only about $400. Came in real handy for diagnosing a commercial Pan/Till module that did some weird Serial Timing. Also does FFT, 16 channel Logic Bus analyzer, Pattern generator, Network analyzer for RF work. Amazing piece of Kit.

For fun I've just logged onto the Digilent Web site. Going to see if I can get the software for my WIN-10 laptop.

edit: Works on WIN-10 laptop.
digilent.com

Analog Discovery 2: 100MS/s USB Oscilloscope, Logic Analyzer and Variable Power Supply

Buy Analog Discovery 2 USB oscilloscope, logic analyzer, and multi-function device that allows to measure, visualize and generate mixed-signal circuits.
digilent.com digilent.com


1720422175332.png
 
Last edited:
My Tek scope decodes all the basic protocols, but you have to pay extra to get this little 2c fidget that you plug into the scope to enable the feature IIRC the fidgets were $1k or some ridiculous price. Well if you examine the little fidget it's just a tiny passive PCB with a few gold fingers that connect the various fingers depending on the fidget. One of the PCB vendors I deal with constantly sends me free PCB coupons, so I made a little fidget PCB to enable the protocols. It took about 15 minutes to make the fidget and I don't get paid $1000 for 15 minutes of work.
 
slow-poke said:
My Tek scope decodes all the basic protocols, but you have to pay extra to get this little 2c fidget that you plug into the scope to enable the feature IIRC the fidgets were $1k or some ridiculous price. Well if you examine the little fidget it's just a tiny passive PCB with a few gold fingers that connect the various fingers depending on the fidget. One of the PCB vendors I deal with constantly sends me free PCB coupons, so I made a little fidget PCB to enable the protocols. It took about 15 minutes to make the fidget and I don't get paid $1000 for 15 minutes of work.
Click to expand...
That might work with my older 2 channel Tek Scope. It does have the little plug in modules. Don't recall if it did serial protocols. The scope is old by today's standards.
In fact to decode CAN bus back in 2000 I had a PC based digital logic analyzer for which you could write add on processing modules. I wrote one to decode not only CAN bus but also our customized CAN bus for power line networking. One of the engineers at LeCroy was so taken with the concept of how I did it he added that feature to their scopes.
 
slow-poke said:
My Tek scope decodes all the basic protocols, but you have to pay extra to get this little 2c fidget that you plug into the scope to enable the feature IIRC the fidgets were $1k or some ridiculous price. Well if you examine the little fidget it's just a tiny passive PCB with a few gold fingers that connect the various fingers depending on the fidget. One of the PCB vendors I deal with constantly sends me free PCB coupons, so I made a little fidget PCB to enable the protocols. It took about 15 minutes to make the fidget and I don't get paid $1000 for 15 minutes of work.
Click to expand...
Like this one? I don't have any plugins for it.

1720462332795.webp
 
Looks like the same port. I might have a spare fidget board, let me know if you want me to look.
9123A6B0-3489-4034-9FE0-4B29E30BE75F.jpeg
 
Last edited:
A bit of a struggle remembering how I set up the math along with using EXCEL to calculate the scaling formula but now it shows pressure. Just a matter of adding a T connection and permanently fixing in the transducer.

PressureTransducer.jpg
 
Next step is to figure out how to add some indicator LEDs to show which set of readings are displayed. Kind of fun to use 35 year old displays with 10 year old controllers and make it all work.
And then use 3D printed enclosures to hold stuff.
Tomorrow I'll go and see if I can get O-Rings for the outlet air water separator. I'd like to put it back and then the T for the pressure transducer. I'm not sure a transducer should be mounted horizontal or below so water could leak into it. Mounted on the top it's in the way of the display.
 
jcdammeyer said:
Next step is to figure out how to add some indicator LEDs to show which set of readings are displayed. Kind of fun to use 35 year old displays with 10 year old controllers and make it all work.
Click to expand...

You are having way too much fun! But you better be careful. Your bride is gunna sense how happy you are out there and reset your priorities.......

jcdammeyer said:
And then use 3D printed enclosures to hold stuff.
Click to expand...

Of this, I am extremely jealous! You guys all keep scaring me to death with your printers but the idea of making custom enclosures is simply intoxicating!

jcdammeyer said:
I'm not sure a transducer should be mounted horizontal or below so water could leak into it. Mounted on the top it's in the way of the display.
Click to expand...

Pressure doesn't have to be measured where there is air flow. You can put it at the top at the end of a T line someplace and it might have the added benefit of stabilizing some of the air pulses.
 
Susquatch said:
Pressure doesn't have to be measured where there is air flow. You can put it at the top at the end of a T line someplace and it might have the added benefit of stabilizing some of the air pulses.
Click to expand...
No worry about pulses here.

It's measuring the air pressure in the whole shop line after the regulator and ball valve. If I shut off the ball valve it takes a while for the air in the system to bleed down. A lot longer now that the old water separator has been removed. Might even be the regulator which is also really old. Or one of the 'A' type quick couplers.

If I mount it vertically on the T where I'd like it's in front of the display.
 
jcdammeyer said:
I want to keep everything close to the tank so nothing sticks out. I'm great at bumping into crap.
Click to expand...

I'm a rather clumsy ox myself. I, was thinking above the readout, or off to one side, not in the front or in your way.
 
You must log in or register to reply here.
Back
Top