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Sensors / Re: HC-SR04 Ultrasonic Range Finder - Random Readings in a Tank
« Last post by Cube on September 17, 2015, 08:52:02 AM »
After a slight change in the code last night causing the HC-SR04 to only perform one scan about every 6 seconds, I checked the salt tank again this morning and the results are now [nada]. Apparently the sensor is detecting the pulse so close to the trigger time that it is saying the distance is 0 cm, which I've instructed the VSAC to discard, so effectively I get no updates from the device anymore. Definitely not what I was expecting. I tried connecting my test sensor directly to the VSAC in case there are other issues (sensor, mounting, location, salt content, etc.) but the results are identical. Next step: Remove the onboard distance-calculating math and send the time differential back to the host for off-board analysis.
Indicators, Displays and Other Human Interfaces / Noritake Vacuum Fluorescent Displays
« Last post by Cube on September 17, 2015, 12:53:45 AM »
A few years ago, a company out of Japan named Noritake was giving away demo VFD displays. All you had to do was send them your address and they would mail you a demo kit, which included a very nice 6 line VFD display. It even included a number of optical filters to change the color of the text from the screen. I love the naked VFD green, though it does look great in just about any color. One of my long term slash back burner plans is to build a display unit based on that screen for some localized feedback from Venturii. With 6 lines and something like 40 characters across, one could pack a lot of information onto their surface.
Sensors / HC-SR04 Ultrasonic Range Finder - Random Readings in a Tank
« Last post by Cube on September 16, 2015, 09:10:33 PM »
After a fair bit of research on the subject, I landed a ten-pack of Chinese HC-SR04 4-Pin Ultrasonic Distance / Range Sensors to test their viability to measure the level of fluids in various containers. Originally intended for an outdoor water fountain, I installed one but never got a chance to test it out before the fountain was deployed. That fountain has been filling my garden with lovely trickling water sounds for two seasons now, but the water level sensor still remains connected to nothing. So it goes with many projects. One other application I had for it, however, employed such a sensor to measure the level of salt in my water softener. You can see my post about the project on the Venturii Blog here.  Over the past couple of nights I have been tinkering with the firmware in the VSAC (and made some significant improvements to the OWI code at the same time by the way...) but still get pretty consistent and random readings from the sensor. It is connected to a stable power supply (and not powered by a USB port.) Each firmware version I try causes me to swap out the Mega so I know it's not the Arduino hardware. The trouble is that some of the readings appear to be correct. With a measuring tape I've determined that the distance from sensor to salt is about 72 cm. My theory goes that as the salt is consumed, that distance will increase; some simple math will allow me to produce a percent full number and I can even set up alerts to let me know when I need to pick up more salt. However, all that is impossible until I can get the sensor to stabilize.

Here is an example of what I am seeing:

After much reading online, I've got two theories I'm going to pursue at this time. 1. The sensor is being polled too frequently. One reader commented to a post on this subject that [they] had encountered this situation where the outgoing pulses are being sent out in such short succession (since you have control over the timing of such pulses via the trigger pin) that it can actually mis-interpret the return of a sound wave from the last pulse as though it were returning from the current sound pulse, resulting in shorter measurements.

The other theory I read about is that a design flaw in the sensor itself can cause sonic disruptions in the air from outgoing pulses to be picked up prematurely by the receiver due to the two components being in too close physical proximity to each other. The reader who made this assertion claims he had resolved this issue by de-soldering the transmitting and receiving transducers and spacing them about 10cm apart. I'm not sure why you wouldn't just de-solder one of the two and leave the other on the PCB, most likely the approach I will take unless the reason for doing both becomes evident through experimentation. The author also noted that doing so did negatively impact measurements at shorter distances, which makes sense, and is likely not an issue for my application.

In any case, the shorter term fix may be in the firmware, I will extend the current "stun" feature to allow greater time between triggers, possibly even user-tuned. If, say, a once-per-second scan of the tank still yields wildly random results, I will sacrifice one of the sensors and attempt to spread the transducers out a bit more. If it does work, it should make for a very useful (and inexpensive) modification to any water softener. Prior to this, the only way I'd really notice I was out of salt was by accumulation of scale on the shower glass, but of course by that time it is too late!
General Discussion / Venturii Presented at the Calgary Mini-Maker Faire 2015
« Last post by Cube on September 16, 2015, 07:14:03 PM »
Making it's world debut this year at the Calgary Mini-Maker Faire,, Venturii went on display showing some of the convenient and energy-saving features it has. Although the Metal Minds table was put together almost last minute, we did manage to pull together some things to show off at this year's show. One of the ideas I wanted to convey was how much products that work on their own can be made better by connecting them together, a concept that is fundamental to the idea of Venturii.

This was the first time I've been to a Maker Faire, and it was pretty amazing to see - not only the number and diversity of local Makers but also just how many people came to check it out! The Metal Minds table was swamped - almost without ceasing - the entire duration of both days. My throat was raw by the end of Sunday evening, but we got to talk to a lot of people and I hope we generated some interest in both automation in general and in the Venturii platform. I hope that many of those people find their way to this forum and can get connected to continue conversations that were started at the Faire.

The feedback received was great, and we a have a lot to work on for next year, some of which is already underway. Please feel free to post pictures from the event; I was so busy the entire time I only got to glance at exhibits that were physically located between our booth and the bathroom, but I know there was a lot of amazing things to see.

Some other links to check out:

Venturii Blog - Journal of my journey through automation and integrating everything.
Metal Minds - Still under construction at time of posting.

John / Cube.
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