Yeah I saw that, I was looking at a pinout and it didn’t mention that. I would be curious if there is a difference in precision between the digital and analog pins for the pwm signal. According the spec sheet it seems like they are the same no?
A couple of red wines and I can’t read your fritzing properly careful with the pot on Vin as that could give 5v to a analogue pin which isn’t good. Best to put it on the 3v3* for a nice stable reading let me check the rest tomorrow when the lines are straighter
Ha! I’ll make that little adjustment now. Enjoy the red wine.
If I squint and close one eye… One of the resistors is in the wrong place and the diode is not quite right too
It’s my phone not the wine!
The diode should be across the motor terminals to stop back emf, at the moment it’s kind of in series
The 1k resistor is a little out of place too if you move it 2 holes left it should be OK and then connect the other end to gnd along with the source pin
Seems like your picking it up pretty quickly won’t take long now and you will be designing and mass producing your own shield
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You’re cracking me up…
Hows this?
Orange wire to the middle pin and it should be sweet
And the yellow to D0… but I guess that’s where it’s meant to be going
Got it! Thanks…More work to do though. Just have to wait for parts.
I also need to figure out a voltage regulator. I have a 12V 1.5A PSU, but I need to get that down for the core. I’ve been using buck converters, but I’d rather have something a bit more simple. I was looking at the LM7805, but it appears they generate a lot of heat. Since this will only be used for the spark, are their other options? What I don’t know is how much the spark will draw once everything is hooked up.
How does this look? Keep in mind, this is for powering the spark core from a 12V PSU.
Options I’ve considered:
1 - Roll Your Own
2 - Buck Converter
3 - DC 12V to 5V Step Down Power Supply Module
I like the RC plane BEC’S as they are tiny cheap light cool and efficient more than enough to run a core
How do those differ from the DC 12V to 5V Step Down Power Supply Module that I mentioned earlier? Also, is there any disadvantage to using a buck converter? In the end I could get the buck converters for around $2.50/ea or less by buying in groups of five or more.
i just have a few of the tiny BEC’s from hobby king that i tacked onto an order when they were $2.20 so thats what i use 
and lots of little modules and lots of wires make things look more technimilogically advanced and geeky
whats your plans with this? how many are you going to make? 5-10 or 100’s? that will be the determining factor i would think.
Well it depends, its probably going to be either a DIY kit for a price, or a bit more expensive version that I build for them. This isn’t going to be a marketed item, just an offer to fellow hobbyists. In the end the point is to make this much more affordable for people in the aquarium hobby. A typical 3 channel doser starts at around $300. So anything that can be done to keep the price lower is better. I want the guts of this thing to look clean and professional, not hacked with different pieces. Does that make sense?
Also, I want the parts to be user maintainable. So if something goes out they can replace it themselves. So essentially is a complete open source system from software to hardware.
I couldn’t find a servo in my box of odds and sods before i left for work so I’m not able to test the 3d printed pump for a few weeks
I’m looking at some different options to keep this affordable, and make it super sweet! Id like to help out where i can and help design and make a shield.
For accuracy and better control of dosing rates I’m thinking stepper pumps would be the way to go, i found these for about $42 each, they look pretty good quality to me and because of the stepper the dose can be as slow as you like
http://www.aliexpress.com/item/one-pcs-new-peristaltic-pump-dosing-pump-with-42-imported-stepper-motor-tubing-hose-pump/1320075703.html
and to control them you could use the cheap and readily available 3d printer motor drivers, i don’t think it would look too hacky to have them as plug in (user replaceable if they blow)
http://www.aliexpress.com/item/5pcs-lot-StepStick-A4988-Stepper-Driver-Heatsink-For-Pololu-Reprap-Prusa-Mendel-RAMPS-3d-printer-parts/1848891176.html
So for a shield we could have a board with a receptacle for the spark and 3 of the stepper drivers, there could be a 3.3v power regulator on board (same as the relay board one) and some headers for motor connections and for manual control options. that way if they want a single dose pump all your supplying is the headers and not all the drivers. Picture the relay board with the pololu stepper drivers instead of the relays, and a couple of extra ports for plugging in extra things
To make it better than the rest of the options available we could add a port for adding a probe or 2, it wouldn’t have to be anything besides a header, that way if you want to add a pH or calcium probe its just a matter of buying the module and plugging it in.
What about temperature probe? even if it didn’t control anything you could have it send a warning to your phone saying the tank is going out of temperature range, could be an indication the heater or chiller isn’t working
And a beeper to let you know when somethings not right? level probes for tank level? or chemical levels? these are all cheap and easy to implement.
Hey @Hootie81, I love the way you think and I appreciate your interest! I’m all about putting effort into continuously improving a project. Steppers do sound good, I’ve always had interest in them, I just figured they would have been too expensive. Currently I want to finish the 12v motors option, which I should have the final parts at end of day today. Once I get that working then I’d love to look further into steppers with you. I did mention to @kennethlimcp that I would like to see some effort put into building a dedicated motor shield for the sparkcore. Maybe this is a good time to do that.
Regarding your probe thoughts, while there is definitely a market for that, I personally already own a high end controller that measures and controls all kinds of things(temp, salinity, pH, water levels, fans, lights, pumps)…it doesn’t measure calcium though, which I’m surprised seeing that those probes don’t seem crazy expensive.
If you have interest in that sort of thing, take a look at Neptune Systems, Reef Angel and Digital Aquatics
One thing that I do have interest in pursuing, that the reef angel does, is dosing calibration. The reef angel is completely open sourced as well based on arduino mega, and there is one gentleman in their forums that writes a lot of code who reached out to me to show me his calibration code. The problem is I’m not sure how to port that over.
I can honestly say I wouldn’t have gotten this far if it wasn’t for the help of @bko, @Hootie81 and @kennethlimcp. I just want throw a thank you to all of you guys, and any one else who has chimed in. Thank you!
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PM me if you need help with the shield
I kind of had in mind a board that would be useful for a few different things, one of which was a 3d printer controller. using the pololou stepper drivers, adding a FET for the extruder and heated build platform. wouldn’t it be cool to push a button on the laptop to send the file to print wireless. that way the probe headers could be used for temp inputs or limit switches. @kennethlimcp was interested in a P+P machine and a board with a few stepper drivers and headers for sensors would be useful.
Ive been looking at the american marine calcuim probes, for $183 including the monitor http://www.marinedepot.com/American_Marine_Pinpoint_II_Calcium_Monitor_Single_Item_Monitors_Controllers_for_Saltwater_Aquariums-American_Marine_Pinpoint_Monitors-AM1121-FITEMOID-vi.html
Im pretty sure they just output a voltage proportional to calcium levels.
As for calibration i remember reading your post about it… i don’t see why its a hard thing to do, pump for a certain time, measure the volume and you have a relationship between time and volume, or the other way as coffee machines do, press a button to start pumping and when you have the required amount of water you push the button again.
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A quick teaser for you before i go to bed!
Been drawing up a spark sized power supply… 6-20V input… And a 2x DC Motor driver shield
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Hot dog!!!
Do you think the shield will do well at low duty?
I see you said 2x DC motor? Does that mean it would only support two motors? Or two motors running at the same time? My project needs three motors total, but only one would ever run at one time.
2 motors at the same time at the moment & Ill try and find a way to make the card addressable, so they become stack-able and use less IO, probably an I2C IO expander on each one as it currently requires 7 lines (2 control lines and a pwm for each motor plus a standby pin). i was looking at a few different chips to do that last night because of all the IO it required… any recommendations from anyone? that way you could do 100 motors at the same time
How much current do your pumps draw at start-up and running? the chip here is a TB6612FNG which should handle 1.2A continuous and 3.2A peak, with up to 15v supply
Im pretty happy with the power supply board, i have 1 or 2 things i will change like where the jumper is fed from. i just dont know how it will effect the WiFi signal being so close, but hope with a card or 2 stacked between it should be ok. you can see a 2 pin jumper in the middle, that’s for a stackable header, so you can hook up 12v to the power supply + and - pads below the USB port and that will supply the board above. the supply itself is the same as the one on the relay shield.
I don’t know how the chip performs at low duty-cycles, in the past if I’m driving a DC motor rated for 5v then if I’m wanting hi torque at low RPM i will use a 12v supply and limit the PWM.
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The motors I'm currently using are 12V, which are not high quality, draw 0.2amps while running and about 0.4amps on startup - again thats when the motors are trimmed back. My meter reads about 4-4.5V at that speed.
Awesome
I have found a SPI I/O expander with PWM control, so with 4 wires we could control many of these cards, i just need to work out the best way to link them together and still have the bus free for other things like SD card, FRAM or displays 
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