Hi,
Excellent, good luck with that.
Cheers, Stub
BTW, nice looking thermal solution… Quick question. Not to worry if not, but I can’t see a network port, would that be easy to add via the normal expansion? Or can we add the 5MP camera to the Portenta and use its wired ethernet from the OpenMV side?
Hi Stub,
Apologies, I have another question, what thickness is the steel you are using, you mentioned on your website it takes roughly 10 minutes for the temperature to stabilise. I’m not sure what way your blackbody works but I’m thinking of using a PID controller along with the SSR, a couple of cartridge heaters and a thermocouple to implement it as opposed to using arduinos or raspberry pi which may be more time consuming. Also given that set points shouldn’t be changed in my system I don’t think I will need much of an interface with it other than seeing the pv and sv which the PID controller would do.
I presume your previous post was not meant for me?
Thanks,
G
Hi,
Its a 3mm sheet. It would be good to know the results of your design and the dual black body…
Hi,
I’ll definitely let you know if it works/if I get a chance to do it.
Thanks,
G
The OpenMV Cam Pure Thermal is just a mashup of everything we already support. Now with the Portenta we will support Ethernet. So, maybe we’ll do a R2 with ethernet later. However, we literally used every I/O pin of the largest STM32H7 package. I think we can reclaim I/O pins by sharing I2C buses however.
Ethernet is tricky to support however. It can only be on certain pins… that conflict with other pins. Enabling it, along with SDRAM, LCD, and camera at the same time is hard.
…
There’s the standard expansion shield interface for the OpenMV Cam on the Pure Thermal Board. The SPI bus on there will do 80 Mb/s. You can’t add ethernet to that directly, however, you could add a wiznet to SPI IC. Or, add an ESP32 with ethernet.
…
Regarding the Portenta… we’re talking with Arduino about making a high quality camera shield for it. With PoE Ethernet.
Hi,
You have been busy! Thanks for the info. I will wait for the Portenta with the PoE and HQ camera shield. Not in a rush, just wanted to know how difficult it would be.
Hi Stub,
Another quick question for you, do you know what the power draw/usage is for the blackbody your using?
Kind regards,
G
Hi,
Yes its 20-25W or so.
If you do a 20°C version, will it be in a colder ambient temperature area?
Hi,
The ambient temperature of the scene will probably fluctuate around 25 - 30 degrees for the most part but the outer limits are 20 and 40. Given space constraints both blackbodies would be relatively close together.
But to answer your question no the ambient temperature wouldn’t/shouldn’t be less than 20. 20 is the absolute minimum for the system.
Cheers,
G
And so what temperature will the 20°C black body be before you power it up?
Yes I think I see where your coming from now…the 20 degree blackbody may need to be cooled as opposed to heated if the ambient temperature is too high. Another thing to think about!
Thanks,
G
Hi Stub,
Apologies for the endless stream of questions, can I ask what sort of a heater element are you using? Is it a cartridge heater or some form of a ptc heating element which seem to be the more power efficient option.
I had initially thought of using a cartridge heater but a ptc heating element may be the better option.
Thanks,
G
Hi,
I used 3 of these at 6V they are fine (with the FET). 5V Heating Pad - 5 x 15cm - RobotShop Other distributors are available, its a sparkfun part.
Out of interest have you checked to see how uniform the heat distribution is on the plate? Or do the three of those heating pads completely cover the back of the plate to mitigate that issue?
Yes (fluke spot meter) and yes - it’s fine for my purposes as the camera is looking for the average in the blob.
Thats great, thanks for the help.
G
Hi Stub,
In terms of your blackbody heating algorithm did you take the approach of providing current to the heating pad if the temperature is not at the set point and then turn off when the temperature is at the set point or did you go much more robust in your approach. Again I was thinking of applying the Arduino as a PID controller and taking an approach similar to Temperature PID Arduino controller tutorial. Im just wondering if you tried this straightforward on/off approach. I only ask as I’m still waiting for parts to be delivered so I cannot try myself yet.
Kind regards,
G
Hi,
Yes I tried the on/off approach and it was not good enough. I didn’t need a formal PID controller though. Four set points around the control point and PWM 90%, down to 40% controlled any overshoot nicely. Not sure if it would be robust enough as it stands for other set points though.
Hi Stub,
I’ve another quick question if thats alright, how did you mount the heating pad to the sheet of steel, did you glue it to it or something as basic as that?
Thanks,
G