Looks like a valve build might be able to happen this weekend! We are pumped to get the Ion firing more effectively. As long as I can get to work on some design we should be able to turn it out this coming weekend!
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I’ve used the Zenith SL-5408 motion activated security light as a motion detector for my Bird Blaster. In version 1.0, I couldn’t get the detector to work off battery power, even though the whole circuit runs at 5V levels. Now that I’ve acquired a little more electronics equipment and knowledge, I thought I’d take another crack at powering the detector from a low voltage source.
I started this round of reverse engineering by drawing out the power supply circuit in Eagle, adding components until I had reached the point where regulated 5V was present in the circuit. At this point, I didn’t notice anything that I hadn’t noticed the last time around. It was fairly obvious where the 5V supply originated, and that the PIR and timing circuit only used the 5V supply. The schematic is shown below. The 22 pin connection shown on the right is the point where the chip on board processor (the brains of the motion detector) is soldered in at a right angle to the main circuit board.
I keep a pair of peafowl as pets. Peafowl (the male in particular) like to look at themselves in anything that’s reflective. They also like to eat potted plants. This leads to a lot of peacock poop and damaged plants on our porch, which leads to me being in trouble with my wife :). Being an engineer, I figured the only reasonable solution would be to make a motion activated sprinkler to discourage them from hanging out near the house.
This was my first real electronics project, starting in the fall of 2011. My plan was to use a motion activated security light, a sprinkler valve from an automatic watering system, and a custom circuit to connect the two.
After getting the simple 555 based MC-2100 driver circuit working, we moved on to a controller with more features. I’d been looking for an excuse to make an arduino-compatible board (here’s a description if you’re not familiar), and this seemed like the ticket.
The initial spec for the controller included the following functions:
- Read user input from potentiometer
- Send the 50ms period PWM signal to the MC-2100
- Sense the lathe’s spindle speed using a magnetic reed switch or equivalent
- Display the spindle speed on a 7 segment LED display
At this point, the controller meets the requirements laid out above. I’ll discuss the implementation of each feature into the controller in the order listed above.
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After discussion with Terry in the comments of previous posts, we came to the conclusion that the MC-2100 wasn’t expecting a full 5V signal at the control signal input (blue wire). As shown in the MC-2100 schematic, the optoisolator on the input (U1) has a 22ohm resistor (R2) in series with it. Applying 5V to the blue wire results in 170mA flowing through the optoisolator, higher than its 50mA rating.
This lead to the conclusion that there must be another resistor in the circuit at the dash panel end of the blue wire. Upon inspection, there is a 240ohm resistor in series with the control signal output on the treadmill’s dash panel PCB. With the series resistance at 262ohms, the current through U1 is now 15mA, a much better current level for reliable operation.
Taking things a step further, it’s possible for the circuit to operate on higher voltage if a larger series resistor is used. This allows us to eliminate the 5V regulator from the circuit, as well as the transistor from the output, which was mistakenly added to allow the higher output current the circuit required without the current limiting resistor.
Here’s the resulting circuit (keep reading, not done yet!):
As discussed in the comments of earlier MC-2100 related posts, Terry has been working in parallel to create a circuit capable of generating the variable duty cycle PWM signal that the MC-2100 requires to operate. He’s written up a very thorough summary of his design process (click for the PDF file).
Terry’s circuit uses two 555 timers (or a single 556), two potentiometers (one is a trimmer), and various capacitors and resistors. This is a great way to get the MC-2100 working without the dash panel if you don’t have a comparator on hand.
I was helped out immensely by receiving a reverse engineered schematic of the MC-2100. That enabled me to examine and begin to understand how the hardware of the controller worked together to control the motor. However, it didn’t have much to say about the algorithms contained in the Cypress PSoC serving as the controller’s brain.
Throughout the process of developing a control circuit to drive the controller, I’ve learned quite a bit about the software in the PSoC, and I’d like to share the information. The best way I can think to accomplish that is to document the timeline of my testing, and comment on the results. There’s a lot to read here, but if you’re trying to figure this thing out, I think it will be helpful. Here goes!
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Now that I have an oscilloscope, I’ve been able to learn a lot more about the circuit I’ve been designing for the MC-2100, as well as the MC-2100 itself. However, a lot of people don’t have access to a scope (even one as old and crappy as mine :)). I’ve had an idea for a method of analyzing a PWM signal without a scope for a while now. Last night, I got some time to test my idea and it worked fairly well, so I figured I’d share it here.
Easy and Effective Way to Measure PWM… Without a Scope! | Hackaday, schoolie, Brian, and 1 other are discussing. Toggle Comments
In response to Terry’s comment on my previous MC-2100 post, I got the breadboard circuit hooked back up for some testing. In doing so, I found a couple things missing in my previous schematic. I also may be backing off calling this version of the circuit done. It looks like there may still be a bit to learn :).
I had someone ask for a copy of the manual, so here it is:
With the goal of expanding our electronics tinkering/troubleshooting capabilities, I’ve had my eye out for a cheap oscilloscope on craigslist or eBay. The search paid off a couple months ago when I picked up two old analog Hitachi oscilloscopes, along with a square wave generator and a couple other vintage items.
The scopes in question are the Hitachi V-152F and V-134, seen below. I haven’t been able to locate any date of manufacture for these things, but they’re completely analog. The 134 even has an analog storage function, which is pretty cool.
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This is another quick update on the MC-2100 PWM controller project. I’ve tweaked the schematic a bit to put the 5v regulator at the beginning of the circuit, which I think is a better configuration. This circuit is currently on a breadboard, and worked great until the connections in the breadboard started wearing out (around a month of occasional use, including our paintball gun build day). Here’s the latest (and probably final) revision:
When I started this project, I wanted to get this circuit working without a microcontroller for the sake of education and simplicity. At this point, I’m comfortable with calling that goal achieved. Now it’s time to move on to more features, like a tachometer and possibly closed loop control!
My current direction with this project is to develop a combined tachometer/speed control for the MC-2100 and my lathe. I plan to use an arduino to measure speed, display the speed via 4 digit 7 Segment modules (salvaged from the treadmill control panel), and send the PWM signal to the MC-2100. At this point, Joe and I have a working version of the code put together, and the circuit prototyped on a breadboard. I’ll update with progress once we’ve got something more final.
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I was wanting to come up with a way to record my guitar among other things with my iPad without having to drop the $180.00 or so on an Alesis iO dock that honestly wasn’t as functional as what I wanted. Plus, I had heard a lot of reviews saying that the iO Dock didnt work with the iPad 3. So, I started scouring the Internet looking for a better solution. That’s when I stumbled upon the iO2 Express by Alesis. I was thrilled when I saw that this device was about $100.00 less than the iO Dock. The only thing stopping me from buying the device was the fact that I would have to modify it a bit to make it work with my iPad (the iO2 Express was intended to be used with CubaseLE on a PC or Mac). After buying it, I realized that I had a little more work to do than what I thought.
To make the device work with my iPad I had to isolate the iO2’s power from the iPad because the iPad couldn’t provide enough current to power the device. So, I opened up the iO2 and removed the existing USB B female jack, making sure to remember which pin was where (i.e. power pin, ground, data+, data-). Next, I made a Franken-cable of sorts to provide +5V to the iO2. I cut the head off of one end of an instrument cable and I also cut the head off of one end of a USB cable leaving the USB A head that normally plugs into a computer. I stripped off the end of both cables to expose the inner wires. On the USB cable there were five wires: Red, black, white, green, and bare. The red wire is the +5V power line, the black is ground, white is data negative, green is data positive, and the bare wire is the chassis ground. The only wires I cared about were the red, black, and bare ones. On the instrument cable, there were two wires. One was the inner insulated wire which went to the tip of the plug and the other was the outer bare wire which went to the sleeve of the plug. I attached the red wire of the USB cable to the tip wire of the instrument cable. I also attached the black and bare wires of the USB cable to the sleeve wire of instrument cable. Finally, I wrapped each connection with electrical tape to ensure good insulation to prevent shorts. On to the iO2. On the PCB of the iO2 I installed a female instrument cable jack. I attached the tip connection to the +5v pin and the sleeve connection to ground (note how this corresponds with the Franken-cable’s setup). Next, I mutilated yet another USB cable again cutting off the head and leaving the A end intact. This time, I wanted the black, white, green, and bare wires. I attached the green wire to the data+ pin, the white to the data- pin and both the black and bare wires to ground. Finally I slapped some electrical tape on there to try and hold everything together and to provide insulation. You can see in one of the pictures where all the wires go. I just attached the bare wire to one of the old through hole mounts for the original female USB B jack.
Beyond the mods to the actual iO2 I had to buy the Apple Camera Connection kit for about $20 on Ebay. I also had to buy a USB hub because for some reason the iO2 won’t work with the iPad without it. It seems almost as if the hub tricks the iPad. That’s the only part of this whole thing that I honestly have no idea why it works. I found that fix by googling some iPad forums. Anyway, when operating the device, use the Franken-cable to provide the iO2 with power. I just plug the USB end into my Apple charger because it outputs +5V (any other USB based charger should work) and I plug the instrument cable end into the jack I installed on the iO2. Plug the USB cable that has its data pins connected to the iO2 into the USB hub, plug the hub into the Camera Connection Kit, and plug the CCK into the iPad and it should work…hopefully.
I’ve really gotten a lot of use out of this setup. I use it for recordings a bit, but much to my surprise, I use it quite a bit more as an interface with an oscilloscope app I found in the App Store. Believe it or not it works pretty well! We tested it against an actual analog oscope to find that the waveforms look the same and measure about the same as well! All in all, I put about $100 into the project which was totally worth it in my opinion.
Just a quick update. I haven’t finished the permanent driver board, but thought I’d upload a better version of the schematic. I’m currently trying to decide if I’ve messed up the MC-2100, or if my soldering just sucks. At this point, I’m getting the motor to come on, but not consistently like it was with my breadboarded circuit. The indicator LED will flash 5 or six times, and the motor starts turning, then the LED goes back solid like it’s not getting signal, and the motor slows back down. I’ve had a couple of occasions where the motor will run up to full speed, so it’s at least close. I can at least confirm that this circuit worked on the breadboard, as shown in the previous post.
I also wanted to post a few of the relevant files I’ve found pertaining to the MC2100.
Here’s the document that describes how the controller is interfaced with the treadmill, and the function of each pin of HD2 on the MC2100. This is essentially the same file that James linked to in the comments on my previous post.
The following file has been extremely helpful in troubleshooting the MC2100 itself as I’ve messed it up along the way. The file was provided by a member of the Home Shop Machinist forums in this thread.
Free treadmills from Craigslist are a great source of DC motors and motor controllers for machine tools. A quick search will yield several examples of people repurposing these motors and drive for drill presses, lathes, and various other equipment.
From what I’ve seen, the MC-60 type controller is by far the most common in low end treadmills (the type you typically can get for free). Three out of the four treadmills that have passed through my garage have had the same MC-60 controller, and nearly identical permanent magnet DC motors. This controller is relatively easily repuroposed as a machine tool drive, as the input is a simple voltage divider circuit driven by a potentiometer. Just take the pot off the treadmill’s dash, mount it to your bench, and you’re up and running.
The MC-2100 proved to be a bit more complicated. My first clue was the all digital dash on the treadmill it came out of. A quick google concluded that the MC-2100 required a 5v PWM signal with ~50ms period. I found a good reference circuit on the All About Circuits forum (Link):
This circuit has two stages. The first is an astable 555 vibrator. Tapping off the capacitor charge pin (Pin 6 on the 555) results in a sawtooth output, with the frequency set by R1, R2, and C. This sawtooth is then fed into a LM393 voltage comparator to convert the sawtooth wave into a square wave.
Here’s my final circuit sketch:
And a quick first test video:
In my opinion, it was worth the effort to figure out because the MC-2100 is a high frequency PWM controller, as opposed to the MC-60 which is an SCR based controller that operates at line frequency. This results in a much quieter motor. Also, based on a couple quick test cuts, the MC-2100 seems to have a higher current capacity.