[Brett]

in reply to: Input signals #3927

Will the osPID do the job?

I’m skeptical that it will. the osPID has a sample time of 250mS. this is more than adequate for things like temperature, level, and pressure, but it’s likely WAY to slow for electricity.

[Brett]

in reply to: Python Interface #3919

I’m curious if anyone has tried to interface with the osPID using Python? Was it straightforward or painful?

If it’s painful, it’s my fault. it should be fairly stright-forward however. PC->ospid communication is binary, with a fairly simple instruction set. ospid->PC com is in the form of strings. the code is fairly-well compartmentalized, and shouldn’t be too tough, unless you’re trying to send setpoint profiles. that will be a little more involved.

[Brett]

in reply to: thermocouple calibration #3912

Woops – I got deleted along with the SPAM! Brett’s put me back.

amazingly embarrassed and incredibly sorry about this. in my effort to keep the forum viagra and porn free, I accidentally got rid of a legitimate user. experienced moderator I am not.

[Brett]

in reply to: thermocouple calibration #3900

Ok. We have found the cause of the issue: we screwed up. Buried in the MAX31855 data sheet there is a reference to a filtering capacitor, even though it’s not on their schematic. We didn’t put it in our design. Luckilly it’s an easy fix, and all units shipped after today will have this issue corrected. However, there are 22 units in the wild that have this issue. We have sent emails to everyone affected, but I want to post this here as well to close out the thread.

If you are affected, you can follow these instructions to correct the issue.

[Brett]

in reply to: thermocouple calibration #3898

we have heard of this issue from one other person, but we haven’t had enough information to nail down a solution. one possible cause that was identified was that it only seems to occur when both the usb and DC power are applied.

can you guys confirm or dispute this?

[Brett]

in reply to: osPid front end 3870e68 compile problem #3894

it was built for windows, but I thought I had taken care of all those “” by using file.separator instead. where are you getting your error?

[Brett]

in reply to: logging #3892

John,

if you run from source you can output to a text file. line 24 of osPID_FrontEnd.pde lets you specify an output path. the frontend will then dump everything that comes back from the osPID into this file. you can easily parse out your signals from there.

there are no firmware differences between v1.2 and v1.5. There are (minor) hardware differences however, so to avoid confusion the firmware contains a specification flag for each.

[Brett]

in reply to: new firmware and frontend #3889

If you’re using the ospid with the max 6675, there’s no real reason to upgrade to v1.6 of the firmware. that version of the firmware is, by default, configured to access the 31855 chip. this conflict is probably what’s causing your issue.

if you want to use v1.6 with your hardware, you’ll need to tell the firmware what it’s connecting to. you do this in io.h. at the top, there are a series of #define statements. un-comment the two that belong to your input & output cards, and comment out the rest. when you build the firmware it will ignore the code for the other io cards (e.g. the the input card with the 31855 chip,) and will keep the code that pertains to your cards.

hope this helps.

[Brett]

in reply to: Thermocouple Digitizer #3887

Why was the chip changed from the MAX31855 to the MAX6675?

strictly logistical. we were faced with either delaying the initial release by 4-5 months, or using the 6675. so we went with the more expensive 6675 just to get the ospid out the door. the 31855 is now available in steady quantities and is used in v1.2 of the input card. v1.2 is what we’re now selling. the 6675 was strictly a first-batch thing.

[Brett]

in reply to: Chlorine dosage #3886

Hi Chuck, sorry this thread slipped through the cracks. the osPID currently does not support 4-20mA on the input or output side, although there are plans in the works for both of those. no idea on timeline though.

[Brett]

in reply to: osPRESSO #3880

with a hint of garden hose and elbow grease… Might need to work on that…

maybe the garden hose part, but elbow grease tastes delicious! thanks so much for posting this. seeing people actually USE what you put out there… well, it’s pretty damned amazing.

I’d love to hear more about this project. from what I can make out in the pictures above, it looks like there’s a lot of custom kit going on. any chance we can get a more detailed description of this awesomeness? (and maybe a few more pics? 🙂 )

[Brett]

in reply to: How does the OsPID modulate its output ? #3884

@redwire the pwm window size is an adjustable parameter. by default it is 5 seconds, but you can make it whatever you like. currently this is the only form of output. it can go either to a relay or a ~3-4V (don’t have the exact number on me) digital pin.

with firmware tweaking and hardware hacking available however, it’s likely that you can do whatever you want.

[Brett]

in reply to: osPID_FrontEnd #3871

Ian, thanks so much for doing the leg work on this bug. I’ve just committed a change to github. I replaced the “\” with File.separator. at runtime the application should now choose the correct slash depending on the operating system.

of course I can only confirm that this works on Windows, but I’m pretty confident that this is the solution.

[Brett]

in reply to: 4…20mA Input or card #3878

4-20mA is currently not possible, but there is a card in development.

[Brett]

in reply to: PID control for motor #3876

this question might be better served over at the diy-pid-control google group. this forum is more about the ospid specifically.

but you posted here, so let’s see what we can do:

looking at your code I don’t really see a separation of the proportional and integral terms i see “error = (P_CTRL)*error;” but then this entire term is summed to old_frequency. instead of output = P*error + I *Sum(error), it looks like you have output = sum(I*P*error).

I would try to sort this out before going any further. about a year ago I posted a series of 7-8 posts detailing how I write a bullet-proof pid algorithm. it’s not going to be exactly what you need, since you’re using integer math and don’t have derivative, but maybe it can give you some ideas.

hope this helps,
Brett

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