Help with DC voltage boost

Discussion in 'Power Electronics' started by home-brewer, Mar 23, 2017.

  1. home-brewer

    Thread Starter New Member

    Mar 3, 2017
    14
    0
    I have a CD101 temperature controller which produces 5.56 DC volts when operating. I would like to boost that voltage to 12 VDC. I purchased a DROK booster, but when I place it in the circuit the LED flashed constantly. There was no documentation with the booster, so I'm wondering what I have done wrong. It's supposed to be able to handle 6 amps.
     
  2. wayneh

    Expert

    Sep 9, 2010
    14,966
    5,434
    It's not clear what you're doing. If you want 12V, use a 12V power supply and forget the temperature controller. I'm sure you need your controller, but my point is I can't understand what you want to accomplish. More details please.
     
  3. home-brewer

    Thread Starter New Member

    Mar 3, 2017
    14
    0
    OK - I'm repurposing an a/c to cool a room for home-brewing. I jumped the thermostat to get the a/c to run continuously, so I need to monitor the coil temperature for freezing. That's where the temp controller comes in. I need to energize a relay when that happens. It's hard to find a 6V NC relay, so I bought a 12V. When the coil freezes, the relay in the TC closes, and I need 12V to energize the relay that will stop the compressor when the NC relay opens.
     
    Last edited by a moderator: Mar 31, 2017
  4. LesJones

    Well-Known Member

    Jan 8, 2017
    1,572
    389
    Can you supply some information on the temperature controller ? The ones I have seen normaly have a set of changeover contacts as an output. If your controller just provides a 6 volt control output it may not be capable of providing enough power via the step up converter to drive your 12 volts relay. Also how much current does the 12 volt relay coil require ?

    Les.
     
  5. home-brewer

    Thread Starter New Member

    Mar 3, 2017
    14
    0
    The temperature controller is a CD101. I'm not sure of the manufacturer. It provides output to power a SSR. The control voltage seems to be 5.6 VDC, and the SSR controls an a/c unit. Since I'm new to electronics I'm not sure about the 12V relay. I do know that no matter where in the circuit I put the stepup it acts up.
     
  6. wayneh

    Expert

    Sep 9, 2010
    14,966
    5,434
    And you want it to instead control a 12V relay? Do you have a 12V DC source nearby, maybe inside the controller? It would be easy to put a transistor between the 5.6VDC signal and your relay, to control power to the relay from some 12V source. If you only have 5.6V available, you need something other than a 12V relay. Do you know how big a load the CD101 is rated for driving? Even a 6V relay might be a problem if it cannot drive the coil current.
     
  7. home-brewer

    Thread Starter New Member

    Mar 3, 2017
    14
    0
    I guess I'd rather concentrate on the issue of the voltage boost. The power requirements of this circuit are minimal, in my inexperienced opinion. If, after I get the issue of the voltage stepup resolved, and the temp controller is another issue, I can deal with that at that time. I don't have a 12 volt supply readily available, but if it becomes necessary I can deal with that. Do you have any thoughts on my stepup issue?
     
    Last edited by a moderator: Mar 31, 2017
  8. LesJones

    Well-Known Member

    Jan 8, 2017
    1,572
    389
    If it is only designed to drive a solid state relay then it will not provide much current. Why not use a solid state relay. From looking at a manual I found on line I think you can reverse the sense of the switching to avoid the need for a NC relay. Also it is a PID controller so it may not be possible to use is like a simple thermostat. You would need to read the manual.

    Les.
     
  9. home-brewer

    Thread Starter New Member

    Mar 3, 2017
    14
    0
    The idea of using a solid state relay is really intriguing. You say you can reverse the "sense" of the relay? Can you point me to that manual? That would take fare of my problem. This PID controller will function as strictly on/off if you set the operating parameters to do that. I would like to look into the ssr, though.
     
    Last edited by a moderator: Mar 31, 2017
  10. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    3,541
    1,286
    What is the relay driving?

    Specifically, what is the voltage and current requirements?

    A quick google search produced over 300 6V relays, with at least one set of NC contacts. To narrow it down requires the data I requested.
     
  11. LesJones

    Well-Known Member

    Jan 8, 2017
    1,572
    389
    This is the link I found for the manual. It was the first hit that the search engine pulled up !

    Les.
     
  12. home-brewer

    Thread Starter New Member

    Mar 3, 2017
    14
    0
    Thank you, Les.
     
  13. wayneh

    Expert

    Sep 9, 2010
    14,966
    5,434
    If you've got lots of power from the existing source, which we don't know yet, then you could consider a DC-DC converter with a 12V output and rated to handle the current required by your relay.
    These converters are cheap on eBay.

    The problem is, if you don't have enough current and power to begin with, adding more components will only make that worse. You might get 12V with no load but not enough current to trigger the relay.

    You need to know the specs on the output in order to determine whether it could work.
     
  14. home-brewer

    Thread Starter New Member

    Mar 3, 2017
    14
    0
    Man, I have wasted so much time going this way. The documentation that comes with that temperature controller was written by someone who had only a passing acquaintance with English and I don't see anywhere in it I can get a specific number on the output. I guess I'll have to tear it all up and try another way. In the meantime I'm having to drink purchased beer. I have a power supply laying around that produces 19 volts, so I guess I could get a stepdown and go from there. Does that make sense?
     
    Last edited by a moderator: Mar 31, 2017
  15. wayneh

    Expert

    Sep 9, 2010
    14,966
    5,434
    Yes, as a way to get 12V it's not bad.

    Have you figured out the various output options? I didn't, but it sounds like you can select various modes and only one of them is a relay control output. I would expect more than 6V there.
     
  16. home-brewer

    Thread Starter New Member

    Mar 3, 2017
    14
    0
    There's a DC output, and a relay output. The DC is what's bouncing around.
     
  17. wayneh

    Expert

    Sep 9, 2010
    14,966
    5,434
    Well yeah, it's not an on/off output, it's proportional. You don't want to use that for a simple thermostat.
     
Loading...