[DIYbio] Re: PCR Heat Blocks

So the result from taking the measures from the gypsum casts showed no major differences. Today I created the new 3D model and drawings for the order and sent it to the Chinese manufacturer to get a quote for the price. The design include wells for 25 tubes, the ground plate is 50 by 50 mm and there is a hole for a temperature sensor in a TO92 housing and two tapped holes for the PCB of the temperature sensor. Anyone who is interested, please send me an e-mail to michael@locustpcr.de with your address. Then I can send you the 3D model and drawing of the block, and, as soon as I know it, also the price and shipment costs. Then you can decide if and how many heat blocks you want and we can go ahead with the order. I will not charge anything on top of the costs, however I think the DIY bio foundation here in Heidelberg (Biotop) will be very glad for a small donation of your choice once it is officially established ;-) .

Concerning the TEC PWM issue: I talked to an engineer from a TEC manufacturer once and he told me that using PWM on a Peltier element in principle not a problem. However you should make sure to use high frequencies (above 60 kHz) because otherwise the product's life time will decrease due to mechanical stresses. That is also in line with my observations: so far I destroyed three TECs one was a very cheap one, one broke after I bang-bang controlled it for a while which means it was switched on and off very often and another one that was run with the default Arduino PWM frequencies (500 Hz/1 kHz) for a while. I did not break any of the four PID controlled ones with high PWM frequencies I am using so far although I regularly apply 100 W+ of electrical power to them. The amount of power they (can) draw depends on the temperature difference across them.

Cheers,
Michael

Am Donnerstag, 12. Januar 2017 15:02:01 UTC+1 schrieb ukitel:

Hi,

Check the message below from alphanoob.
If you want to order one, you could join our order!

On Wednesday, 11 January 2017 10:32:34 UTC+1, Kermit Henson wrote:

Hi ukitel, 

Can you give more info about the chinese custom milled aluminium block? Cost per unit, time, provider... ?

El martes, 10 de enero de 2017, 16:22:42 (UTC+1), ukitel escribió:

Hey,

Here at the DIYbio community of Heidelberg, we have actually developed a working PCR machine on the cheap (300€) and we have replicated successfully several time our design.

For the heat block, we tried different approaches: we bought our own drill bit, which worked but it's quite expensive. Now we just ordered a custom milled aluminum block from some chinese company which also worked (more or less).

If you are still interested, we would be very happy to discuss about it!

On Wednesday, 4 January 2017 15:14:03 UTC+1, Trenton Adams wrote:

Thanks again!  I'm going to check those out.  It'll be a lot nicer than my breadboards and copper clad :D

On Wednesday, January 4, 2017 at 12:51:26 AM UTC-5, Andrew Barney wrote:

Well it was several years ago now. But basically i designed it in EagleCAD when EagleCAD was the Electronics CAD software of choice for the hobbyist scene with arduinos, adafruit, sparkfun, etc. Especially for those of us who use Linux (or Macs) as EagleCAD is cross platform and has a free version. I think it just got bought by Autodesk bytheway and there still should be a free version and continue to be cross platform. Some will be quick to mention KiCAD as a fully OpenSource alternative, and that might be a usable program now, i wouldn't know, all i know is back then it kinda stunk and i had already gotten used to EagleCADs quirky interface. Some places still like EagleCAD files though, like Sparkfun i think.

But anyway, regardless of what software is used it's easy to export the necessary Gerber Files and send them off to any PCB prototyping services. It's even more fun when it's an actual solderable PCB with electronics pads and component silkscreen outlines. But yeah. Since i seem to have both Purple and Green PCBs for this i think i actually used two different services. Originally the Sparkfun PCB service which is now closed but merged into the Dorkbotpdx service. The SeeedStudio PCB service isn't bad though. Actually i think i have the original EagleCAD (and maybe gerber) files for the board somewhere on my backup HD if you'd like a copy. Just let me know. It was originally intended as an Open Hardware type thing, despite it never being finished. Not was i sure anyone would actually want to copy it. But hey that's where its at. Sorry for the long winded explanation.

-Andrew

On Tuesday, January 3, 2017 at 1:36:53 PM UTC-7, Trenton Adams wrote:

Oh that's slick!  I'll have to look into using a forced air system.  

How did you manufacture that custom PCB? It looks good!

On Wednesday, December 28, 2016 at 2:24:21 PM UTC-5, Andrew Barney wrote:

I guess this is as good an opportunity to jump in. I too would like to build my own PCR system or two on the cheap. I'd like one to have a nice aluminium heat block like the others, but the other system would not necessarily need one. If still using a "heat block" one possible idea might be to use a high thermally resistant plastic, perhaps even 3D printed. There are some interesting filaments that are available now.

In more in tune with a response to your third question though i will add that John Griessen i think is working on an air-pcr system that requires no heat block at all. Actually several years ago i was working on my own DIY hot air PCR system that i never finished. In my case though i designed a simple PCB that had holes to hold the PCR tubes. Since it was a PCB it has a small layer of copper (i think in both sides) that may help with thermal conductivity, but it's really an air PCR system partially inspired by the original Light Bulb PCR project. Here are some photos of it still in it's unfinished state. I probably could get it working if i put rubber flaps on the front to help keep in heat until the exhaust fan kicked on, removed or bypassed the thermal cuttoff switch to allow it to reach 95degrees, and finish programming the Arduino that controls it.

http://i1010.photobucket.com/albums/af224/keen101/electronics/DSCF8042_zpsgtuhalox.jpg

http://i1010.photobucket.com/albums/af224/keen101/electronics/DSCF8045_zpsrvljicmv.jpg

http://i1010.photobucket.com/albums/af224/keen101/electronics/DSCF8046_zpsoeuyw0r8.jpg

http://i1010.photobucket.com/albums/af224/keen101/electronics/DSCF8047_zpsrht3xqq0.jpg

On Tuesday, December 27, 2016 at 9:35:00 PM UTC-7, Trenton Adams wrote:

I'm looking at putting together a thermal cycler all cheap like. The problem I've run into is finding a heat block for the tubes. I've found them online for $100+ for a professionally made one, or making a substandard one out of scrap aluminum and best effort drilling. I'm not really happy with either of these solutions. And started doing some online searching. I found the link to the GaudiLabs Drill bit diagram from these forums, but no way to directly purchase one.  So this leads me to a few questions.

1.) Am I missing something? In other words is there a cheaper place to purchase heat blocks, the drill-bit, or another method that would work well?

2.) If the answer to #1 is nope. Is this a problem that others are running into? If so how are other's solving it?

3.) If there just aren't any good solutions or alternatives, is this something that the community would be interested in if I spent the time to come up with a solution?  

Thanks!