Digital Tachometer for record player (LCD display)

Interesting... This seems like a much more appealing/approachable project for a noob like myself to get my feet wet than the 4 phase sinewave generator power supply. I did manage to track down and order a Falcon, since I just don't have the necessary skill for that other project yet, which leads me to another question...

@Pyramid: Since the Roadrunner has become unobtanium, what would be involved in mimicking the auto-adjust integration feature with this DIY tach? Did you have a specific proprietary interface between the units? Is that something you would be willing to publish since you are no longer selling devices and more interested in DIY? And for that matter, is it something that you might integrate into your protected firmware in the SG4 so that other daring DIYers could throw together integrated auto speed controllers, while still keeping your I.P. under control?
 
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@Pyramid: Since the Roadrunner has become unobtanium, what would be involved in mimicking the auto-adjust integration feature with this DIY tach? Did you have a specific proprietary interface between the units? Is that something you would be willing to publish since you are no longer selling devices and more interested in DIY? And for that matter, is it something that you might integrate into your protected firmware in the SG4 so that other daring DIYers could throw together integrated auto speed controllers, while still keeping your I.P. under control?

The communication protocol is very simple:

The tach sends the display reading in ASCII readable text in the format XX.XXX[cr][lf]

The data is RS232 level 9600N81. Data is received by the PSU on the ring terminal of the 2.5mm connector (Tip/Ring/Ground).

As far as the DIY version, I hadn't considered it as the capability is unique and proprietary. It would require additional hardware, re-CADing the PCB and firmware change. I don't know that it is necessary at this time.
 
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I finally ordered an official Arduino Starter Kit so that I can learn enough to ask better questions going forward.

I see that tauro0221 is using an IR sensor due to interference with his deck when trying to use a hall sensor. Given that I'm running a VPI (Scout Jr.), what would the trade-offs be trying to use IR or hall effect under the platter? Would hall effect be more accurate and/or reliable in low light? If hall effect would be better in my case, what would be the difference between the following?

https://www.amazon.com/dp/B01NBCKRC4/
https://www.amazon.com/New-Hall-Sensor-Module-Arduino/dp/B009M86TFG/

I'll wait to ask further questions on the actual tach/Kludgerunner build once I've had a chance to run through the tutorials and learn more about how to use the kit. :p
 
Hi,
The difference it is that one has an op-amp and the other does not. The op-amp will make it more sensitive that the one without the op-amp. My problem with the hall effect was because the use of stepper motor to drive the platen. I used a magnet but the pulses to drive the stepper motor was causing interference and was getting extra pulses. That's make me to switched to the infrared sensor. Just glue a 1/4 reflective stripe or paint a black stripe in the platen and you get a clean pulses every time using the infrared sensor.
 
I've finally started tinkering with the starter kit. Since I still have reflective tape from one of those cheap handheld laser tachs, and a black rubber(?) coating on the underside of my platter, I may just give the IR approach a try. I'm looking at this due to price and number of backup components: https://www.amazon.com/gp/product/B0725QS24Z (I would likely use the capacitor you recommended, since I don't have much faith in these being that high quality).

Anyone have/know of a project box that allows mounting the LCD on the "front", with enough room for the Arduino, breadboard, and wires? Perhaps with a built-in switch? My local Radio Shack just closed down last month, so I have to hunt for parts online. Doh.

@Pyramid: for turning a 2.5mm connector into a serial cable for the Falcon, would the Tip connection go to 5V (Ring connector going to one of the output ports on the Arduino)? I just want to make sure I don't fry anything. This seemed cheap enough to cut and strip for the connection: https://www.amazon.com/gp/product/B00291F4RM/

Apologies for the newbie questions.
 
@Pyramid: for turning a 2.5mm connector into a serial cable for the Falcon, would the Tip connection go to 5V (Ring connector going to one of the output ports on the Arduino)? I just want to make sure I don't fry anything

The connection on the Falcon PSU is 3.5mm, not 2.5mm as I posted in error previously. The tip connection is not used between the PSU and the tach. The ring connection would connect to the TxData output of the Arduino, RS232 level 9600N81, and is the RxData line into the PSU. Shield is ground.
 
Thank you both. Very helpful. I may go for that enclosure to keep my cat from nipping any more wires, even if it won't fit under my plinth as I might prefer. I'm reading up as much as I can to ask better questions, so please bear with me.

I see that in tauro0221's diagram, port 1 is being used to send data to the LCD. I assume this could be any port assigned in output mode (ie: port 3)?

@Pyramid: would a direct wiring from Ring connection to an I/O port on the board (ie: port 4, not being used by LCD) be adequate on the hardware side, or would I need to either use an RS232 shield (ie: https://www.amazon.com/Distributed-By-MCM-83-15630-Shield/dp/B00I6O9UKI with custom DB9 to 3.5mm wire) or do a DIY wiring (ie: https://www.arduino.cc/en/Tutorial/ArduinoSoftwareRS232 )?

I'm less concerned about the software end of things. That's more my comfort zone, even if I haven't written any significant C code since about 2002. I'll certainly share any updates and refactoring I might do once I get to it.
 
Hi,
If you use the serial LCD display you can the pin 1 it is the TX pin from Arduino. This will allow you to be able to send data directly to the display when you do a Serial.print. Doing so you will output to the IDE monitor. Now if you use the liquid cristal display then you can use any other pin.
 
@Pyramid: would a direct wiring from Ring connection to an I/O port on the board (ie: port 4, not being used by LCD) be adequate on the hardware side, or would I need to either use an RS232 shield (ie: https://www.amazon.com/Distributed-By-MCM-83-15630-Shield/dp/B00I6O9UKI with custom DB9 to 3.5mm wire) or do a DIY wiring (ie: https://www.arduino.cc/en/Tutorial/ArduinoSoftwareRS232

Not that familiar with Arduino hardware, but it appears the Uno PCB TxD and RxD are TTL level, not RS232. As tauro0221 noted, if you are using the TxD line to communicate with the LCD, you will have to use other ports for communication with the Falcon. The link to your DIY wiring uses any port for the IO and uses software delay routines to generated 9600 baud. Either method requires level translation from TTL to RS232 so you will need to use the RS232 "shield" or construct your own using a MAX202 chip or equivalent driver.
 
Not that familiar with Arduino hardware, but it appears the Uno PCB TxD and RxD are TTL level, not RS232. As tauro0221 noted, if you are using the TxD line to communicate with the LCD, you will have to use other ports for communication with the Falcon. The link to your DIY wiring uses any port for the IO and uses software delay routines to generated 9600 baud. Either method requires level translation from TTL to RS232 so you will need to use the RS232 "shield" or construct your own using a MAX202 chip or equivalent driver.

Check! Will probably go the "shield" route just to keep it clean and build a DBP-to-3.5mm TRS cable to talk to the Falcon. Then I could get a panel-mount 3.5mm socket for connecting to the sensor and just hardwire it to the sensor pins (10 sensors for $4? Who cares if a wreck one). I'll check with that ebay seller to see if his variant for the ethernet shield can be modified for the DB9 connector instead.

Thanks a lot for the feedback, gents! Will update with progress when I make some.
 
Thanks, tauro0221. I did end up ordering one of those, but hopefully I'll be able to make due with the LCD in my starter kit as a starting point.

I also ordered this RS232 shield (I like the idea of the prototyping area): https://www.amazon.com/gp/product/B00N4MKVFK/

Also ordered this DB9 connector, since it only provides the necessary connectors for turning a spare headphone cable into a serial wire for the Falcon: https://www.amazon.com/gp/product/B018HY79Q8/

Since I'm impatient with the long delivery times of the cheaper ebay parts, I went this route for IR sensors (10 is ridiculous, but good to have spares that I can share with others): https://www.amazon.com/gp/product/B01I57HIJ0/

Most of the necessary parts should arrive by tomorrow, so hopefully I'll be able to dive in this weekend and try to get something functional. I'm going to hold off on trying to make it pretty and just focus for now on making it WORK. :p
 
No progress yet on my end (busy weekend), but I did spot this for anyone wanting to deal with fewer wires: LCD Keypad Shield, 1602 Display For Arduino Uno, Mega 2560 - Blue / White - USA

You'd still have to install the sensor connections on the top, but otherwise it'd be good. Other versions of an LCD shield don't have the sockets on the board, so you'd have to improvise how to install a sensor. Is there some kind of 90 degree pass-through header anywhere? It'd be nice to be able to just install sensor connections with connectors between the Arduino and whatever shield might be on top of it (ie: LCD), routing the cables out of the gap between them. (I just really don't want to have to solder anything if I can help it: my cats are already way too curious)
 
So here's my first pass at this. Not quite right yet, but a start. I used the basic LCD, so more wiring and ports were necessary, but it's working.

It does indeed seem that Digital port 3 is needed for the sensor interrupt. Weird. I tried port 13, and that didn't work. Normally the LCD would take up ports 12, 11, 5, 4, 3, and 2, but I shifted some of them up for the sake of the sensor.

I did not use a capacitor to clean up the pulses, I don't know if that is what's screwing up the calculation. Here it is in action: https://instagram.fphl2-4.fna.fbcdn...358_1354713571261332_880029362907250688_n.mp4

I did some refactoring on the code posted by tauro0221 to clean up some text, change display setup, and commented out the power switch portion (trying to keep it simple), as well as removed unused code.

Any idea where I may be going wrong on the interface or calculations, here? I tried to leave the actual functionality alone. Thoughts?
 

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Hi,
You need to add the capacitor. For some reason I found out that I does not worked too good without the capacitor. Arduino only use pin 2 and 3 for interrupts. I need to find my last update of the sketch. I did some update to it to keep the reading more stable. I soon found it will post it. That it is why I recommended the use of the converter lcd parallel to I2C. It use only 2 lines instead 6.

link to the I2C converter.:IIC/I2C/TWI/SP??I Serial Board Module Port For Arduino 1602 LCD 2004 LCD Display | eBay


" from Arduino reference manual
Board Digital Pins Usable For Interrupts
Uno, Nano, Mini, other 328-based 2 , 3"
 
Hi,

to: Packgrog

I checked your sketch and it is the latest on. See if by adding the capacitor at the sensor between the output pin and ground will clear the pulse. I think another member had the same problem and fixed the problem by adding the cap. He got his Rpm display project running using my last sketch.
 
Yeah, I have the LCD with serial board that you linked earlier on its way to me, but that won't arrive until some time in July, possibly August. But, I can make do for now with the current setup. It works, but I just needed to move some of the connections. That said, the LCD Keypad Shield that I mentioned previously SHOULD STILL WORK, as it apparently uses digital pins 4, 5, 6, 7, 8, and 9, (and A0 for the buttons) leaving 2 and 3 open for sensors. I did not order this one, though.

I have so far left the RS232/485 Shield off, as sketches cannot be loaded when that shield is plugged in (I think it blocks ports 0 and 1, needed for uploading sketches).

Sadly, even without the RS232/485 Shield installed, the whole kit is too tall to fit under my plinth, so I'll have to place it on top of my phono preamp. Hopefully this won't introduce any EMI/RFI. I should have enough cable length to get the sensor and serial cable where they need to be.

For a pulse-cleaning capacitor, would a 100nF cap work better/worse? My kit has only 5 x 100nF, 3 x 100uF, and 5 x 100pF capacitors, and as I've said, I no longer have a Radio Shack nearby. Please bear with me, here: my last circuitry class was over 20 years ago. :p