https://joeraut.com/posts/peltier-mini-fridge/
Pelitier is commonly dismissed by HVAC ( Heating ventilating Air Con ) guys as too inefficient to compete iwth gas compression for cooling. However two things:
Coupling the semi to the load matters immensely. You can heat or cool a thermal interface and measure the temp with a themocouple and figure the thermal resistance in W/cm^2 or mm^2 etc.
So you can work with HEAT more easily, then just multiple by -1 * and design the cooling variation. Of course, just turn the voltage around the cooler heats, anyway...
So, yowling the semi is not doing enough starts with how your load gets to free air. If its lossy, thats a place to fix it. TRY COPPER NOT ALUMINUM, etc dabs of conductive goop, etc.
Also, Peltier is unusually sensitive for efficiency to % of max load. if you only use it to 10% of its designed max, its far more efficient then 80%. So *if* you want efficiency ( rare in a lab, but possible ) OVERSIZE the part and run it at a smallish percentage.
For variable temp at high precision, use PID thinking, that is approach the final temp with a duty cycle that changes of a variable part like a 555 timer of better yet a ARDINO or other few component Single board computer postage stamp part.
If the load and ambient temp is known a variable resistor or time chip is probably ok for a tolerance of +- 2 C.
Even if you make a self controlled, closed loop you have to calibrate it occasionally before you can trust it. So really,, a simple control approach is probably ok, you should have independent temp measurements anyway for any serious work.
Pelitier is commonly dismissed by HVAC ( Heating ventilating Air Con ) guys as too inefficient to compete iwth gas compression for cooling. However two things:
Coupling the semi to the load matters immensely. You can heat or cool a thermal interface and measure the temp with a themocouple and figure the thermal resistance in W/cm^2 or mm^2 etc.
So you can work with HEAT more easily, then just multiple by -1 * and design the cooling variation. Of course, just turn the voltage around the cooler heats, anyway...
So, yowling the semi is not doing enough starts with how your load gets to free air. If its lossy, thats a place to fix it. TRY COPPER NOT ALUMINUM, etc dabs of conductive goop, etc.
Also, Peltier is unusually sensitive for efficiency to % of max load. if you only use it to 10% of its designed max, its far more efficient then 80%. So *if* you want efficiency ( rare in a lab, but possible ) OVERSIZE the part and run it at a smallish percentage.
For variable temp at high precision, use PID thinking, that is approach the final temp with a duty cycle that changes of a variable part like a 555 timer of better yet a ARDINO or other few component Single board computer postage stamp part.
If the load and ambient temp is known a variable resistor or time chip is probably ok for a tolerance of +- 2 C.
Even if you make a self controlled, closed loop you have to calibrate it occasionally before you can trust it. So really,, a simple control approach is probably ok, you should have independent temp measurements anyway for any serious work.
The URL above shows a DIY approach for a cooler.
Regs
Daniel B. Kolis
-- You received this message because you are subscribed to the Google Groups DIYbio group. To post to this group, send email to diybio@googlegroups.com. To unsubscribe from this group, send email to diybio+unsubscribe@googlegroups.com. For more options, visit this group at https://groups.google.com/d/forum/diybio?hl=en
Learn more at www.diybio.org
---
You received this message because you are subscribed to the Google Groups "DIYbio" group.
To unsubscribe from this group and stop receiving emails from it, send an email to diybio+unsubscribe@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/diybio/eaa03e67-72c3-4423-aefe-70648fa61696n%40googlegroups.com.
0 comments:
Post a Comment