3 ms·

I've been given different prices on that. Some people say it's just $0.50, some claim it's more than $10 to buy PIDs in bulk.

by chewxy 13y ago

tptacek 13y ago
I've never done a PID from scratch, but a friend of mine did for a home espresso setup. I'm suggesting, instead of pricing a PID part, you price the components of a PID. I think the SS relay might be the most expensive part there.
- chewxy 13y ago
  You have a point. Costing the components of a PID might actually be better. That said, a PID controller for my espresso machine cost about $200, but that was everything packaged in nicely.
  - tptacek 13y ago
    That's an insane price.
    - sk5t 13y ago
      The espresso machine kits traditionally use industrial PID controllers from Fuji and the like, which (did and still do) cost about $200. It looks like there are lots of nice $35 options now... neat.
  - moocowduckquack 13y ago
    A mechanical spring thermometer that goes from 0 to 120 degrees C costs ~£3. Add a microswitch and a relay and you should be fine. http://www.ebay.co.uk/itm/Budget-Surface-Pipe-Thermometer-/370988569892?nma=true&si=M5EdqCeNKH%252BlwMGT0tsvpjbGigQ%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557 http://www.ebay.co.uk/itm/Budget-Surface-Pipe-Thermometer-/3...
- HeyLaughingBoy 13y ago
  As your comment above says, the PID loop is probably just an MCU, sensor (for boiling water a diode sensor is probably fine and cheaper than compensating a thermocouple), and a relay and those are relatively inexpensive components. However, a bimetallic strip rated to switch the current directly is likely an order of magnitude cheaper.
ChickeNES 13y ago
A third option after PIDs and mechanical is to use an opamp and thermistor to control the temp: https://math.temple.edu/~cmartoff/teaching/ph22109/thermistor.pdf https://math.temple.edu/~cmartoff/teaching/ph22109/thermisto... or one of these: http://pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/DS005701.PDF http://pdf.datasheetcatalog.com/datasheet/nationalsemiconduc... (discontinued, but I'm sure there is an equivalent made) I bet this thing: http://www.thinkgeek.com/product/e60d/ http://www.thinkgeek.com/product/e60d/ uses one or the other, given the analog control.
dagw 13y ago
Last time I bought a PID I paid $12 +shipping for a no-name Chinese one. And that was with a case, display and controls. If I just wanted the core components, I think they where about $5.

I've been given different prices on that. Some people say it's just $0.50, some claim it's more than $10 to buy PIDs in bulk.

by chewxy 13y ago

I've been given different prices on that. Some people say it's just $0.50, some claim it's more than $10 to buy PIDs in bulk.

tptacek 13y ago

I've never done a PID from scratch, but a friend of mine did for a home espresso setup. I'm suggesting, instead of pricing a PID part, you price the components of a PID. I think the SS relay might be the most expensive part there.

chewxy 13y ago
You have a point. Costing the components of a PID might actually be better. That said, a PID controller for my espresso machine cost about $200, but that was everything packaged in nicely.
- tptacek 13y ago
  That's an insane price.
  - sk5t 13y ago
    The espresso machine kits traditionally use industrial PID controllers from Fuji and the like, which (did and still do) cost about $200. It looks like there are lots of nice $35 options now... neat.
- moocowduckquack 13y ago
  A mechanical spring thermometer that goes from 0 to 120 degrees C costs ~£3. Add a microswitch and a relay and you should be fine. http://www.ebay.co.uk/itm/Budget-Surface-Pipe-Thermometer-/370988569892?nma=true&si=M5EdqCeNKH%252BlwMGT0tsvpjbGigQ%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557 http://www.ebay.co.uk/itm/Budget-Surface-Pipe-Thermometer-/3...
HeyLaughingBoy 13y ago
As your comment above says, the PID loop is probably just an MCU, sensor (for boiling water a diode sensor is probably fine and cheaper than compensating a thermocouple), and a relay and those are relatively inexpensive components. However, a bimetallic strip rated to switch the current directly is likely an order of magnitude cheaper.

ChickeNES 13y ago

A third option after PIDs and mechanical is to use an opamp and thermistor to control the temp: https://math.temple.edu/~cmartoff/teaching/ph22109/thermistor.pdf https://math.temple.edu/~cmartoff/teaching/ph22109/thermisto... or one of these: http://pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/DS005701.PDF http://pdf.datasheetcatalog.com/datasheet/nationalsemiconduc... (discontinued, but I'm sure there is an equivalent made) I bet this thing: http://www.thinkgeek.com/product/e60d/ http://www.thinkgeek.com/product/e60d/ uses one or the other, given the analog control.

dagw 13y ago

Last time I bought a PID I paid $12 +shipping for a no-name Chinese one. And that was with a case, display and controls. If I just wanted the core components, I think they where about $5.