How to read this Peltier device chart - Page 1
Forum section: electronics / beginners

author: metrologist
author_rank: Super Contributor
timestamp: August 12, 2022, 06:53:36 pm
content: I'm looking at the 50C hot side chart. What confuses me is that if I follow the 12V line and consider the current curves, it looks like less current is needed for a greater delta T.I measure input of 12V @ 3.3A to the device. I'm using a quality AC-DC SMPS brick that is rated 12V 5A, but for some reason it's not putting out its 60W. The heatsink is hot right next to the device but I can leave a finger on it without discomfort. I have a good thermal transfer pad to the heatsink and a small tin of water on the cold side, and it feels about refrigerator cold. I was expecting to see it freeze.Given the 40W input above, if I look at the lower right Qc chart where 3A intersects 40W, delta T is 0. Further, it's like the current curves are sloped the wrong way.https://peltiermodules.com/peltier.datasheet/TEC1-12706.pdfEdit: I just measured resistance starts at 2Ω but climbs up to 7Ω when at ambient.

author: emece67
author_rank: Frequent Contributor
timestamp: August 12, 2022, 08:10:15 pm
content: .

author: metrologist
author_rank: Super Contributor
timestamp: August 12, 2022, 08:46:08 pm
content: OK, so if I want to freeze a block of something and keep it there, I have to know something about its heat transfer to the environment.I'll know I can keep the hot side at 50C with some regulated sink system (i.e., fan control)then I'll know I want dT of 50C, and I can use 1.5A @ 5V, 3A @ 10V, 4.5A @ 13V, etc.But I'll have to use the second chart to know what current I need to pump the equivalent heat power, which is over 3A @ dT of 50CSo my water did not freeze because there was too much heat transfer into my tin and system on the cold side.OTHeat transfer was my least favorite course, and probably because the professor was a tenured penis. Every semester the kids that failed the semester before would circulate a petition to have him removed. He was a bold MF'er, would proudly announce at the beginning of the semester that half the class would not pass. And he was right. He also justified the difficulty of his program, meaning it was so hard that nobody could get 100% because if they did, he would not know how far they really could go.

author: emece67
author_rank: Frequent Contributor
timestamp: August 12, 2022, 10:57:33 pm
content: .

author: metrologist
author_rank: Super Contributor
timestamp: August 13, 2022, 12:00:42 am
content: Quote from: emece67 on August 12, 2022, 10:57:33 pmMight not be getting the point. To make heat xfer to env from cold side big is to put a hot plate there, and that makes dT low? I see a huge dT always. It's never cold enough and always too hot. When I was using a large sink. I put a fan on it and the the sink cooled a lot, and the cold was not as much. ?This is now, a different setup using a CPU cooler with ambient desk fan... Right now I just want to see a blob of water right on the Peltier device freeze. I saw it on YouTube.

author: metrologist
author_rank: Super Contributor
timestamp: August 16, 2022, 12:22:12 am
content: I looked into heat transfer through my thermal pad and heatsink I was using. The pad can transfer 240W heat energy, and the heatsink was ~40W as passive. I added a couple fans to the heatsink, and I have ice, even running @ 10V & 2.85A

author: metrologist
author_rank: Super Contributor
timestamp: August 16, 2022, 12:42:14 am
content: One more pic because it's fun. Still doing the business @10V.

author: metrologist
author_rank: Super Contributor
timestamp: August 19, 2022, 01:32:36 am
content: So I got my tin out and build an insulation box. Filled it half way with 20ml water. If I calculate correctly, it takes a total of ~3/4Whr to bring the water from 25C to 0C solid. The system ran for 1 hour @ 40W to do so, or about 1.8% efficiency, or about 1 cent US at current energy costs (not including losses of the power supply).

author: MrAl
author_rank: Super Contributor
timestamp: August 19, 2022, 06:08:53 pm
content: Quote from: metrologist on August 12, 2022, 06:53:36 pmHello,From what i can gather from your post you have to consider the power not just the current.For example, 3 amps at 8 volts is 24 watts, but 3 amps at 9 volts is 27 watts.If you just look at the amps it looks like it gets magically better at a higher differential temperature.