Hi, I am a student currently taking a STEM Capstone class where each student comes up with an idea for a project and works on it for the rest of the year. I have decided to make a PCR, Polymerase Chain Reaction Machine, which heats up the DNA to 95ºC to split the strands, cool it to 55ºC so the primers can bind to the template strand, and then heat back up to 72ºC to synthesize a new strand. This process is run a total of 40 times. However, I am having difficulties getting the heater to work, a vital part of my project. I have tested out the heater with an external power supply which worked, but when it is in a circuit, it does not work
I first tried using:
SPARKFUN Heating Pad - 5x15cm
DS18B20 Temperature Sensor Temperature
N-Channel 1 MOSFET Pin
however, that did not work as I could not get the heater to heat up
I am now researching a relay circuit using a:
SPARKFUN Heating Pad - 5x15cm
5V Battery
2 Channel DC 5V Relay Module
If anyone could advise me on how to wire this or a different approach, that would be greatly appreciated. Thank you and I hope you all are doing well!
Can you post an annotated schematic of your project, include all connections, power, ground, power sources and note any wire over 10"/25cm in length. Do not run the heater wires through the prototype board or connect to the Arduino.
You won't find that it will make very much heat for very long.
A real power supply.
Is the relay opening and closing the way you planned? You shou,d be able to hear it, and/or use your ohmmeter to see the relay contacts open and close.
Please post complete sketch you've been working with.
You may also benefit from writing a simlple sketch that just "blinks" the relay pin on and off slowly, to get just that functionality locked down.
This post is getting old, but all PCR machines, including DIY-oriented ones like "open PCR" use Peltier modules for fast cooling. In the old days, they used actual mini-refrigerators to pump cold fluid through the tube inserts. And before that they used actual three pots of water and a "turntable" that moved the tubes around.
Youl still need a regular heater for the lid (so your efforts are not wasted), unless you want to use mineral oil to prevent evaporation of the reaction mix.
