Shop OBEX P1 Docs P2 Docs Learn Events
DS1620 problems — Parallax Forums

DS1620 problems

TCP71TCP71 Posts: 38
edited 2010-11-25 15:28 in Propeller 1
I'm starting to think I picked the wrong temperature sensor. I have a DS1620 mounted in a control box down a 10foot run of cable. It and the propeller are 3.3V VDD. When I hook my RST,CLK and DQ pins directly (or through resistors) to the propeller, the output voltage high=0.8V and low is at ground. Do I need some pull up resistors on these lines to make things work or am I missing something here. I never pull data from the 1620 because my RST line can't ever get high enough to trigger things. Any help appreciated.

Comments

  • ElectricAyeElectricAye Posts: 4,561
    edited 2010-11-25 11:41
    Maybe check out the schematic on the following page:

    http://www.selmaware.com/stampplot/users/roof_temp_project_files/roof_temp_project.htm

    Also, see page 11 of this:

    http://www.ocf.berkeley.edu/~daradib/chsntech/review/science/robotics/applied-sensors.pdf
  • kwinnkwinn Posts: 8,697
    edited 2010-11-25 11:48
    It would be a good idea to post the object or code you are using.

    With both chips connected to 3.3V and the prop providing the signals pullups should not be required. Read the data sheet carefully though, the software interface is not simple.
  • ElectricAyeElectricAye Posts: 4,561
    edited 2010-11-25 11:51
    There are some code examples posted in the OBEX:

    http://obex.parallax.com/objects/search/?q=ds1620&csrfmiddlewaretoken=7e71dcb8f31369ee7bc12812e5bd1444
  • TCP71TCP71 Posts: 38
    edited 2010-11-25 12:22
    I'm just using the DS1620demo.spin from the object exchange. It's showing as 0C or 32F on the LCD display and I can see signal levels from the reset and clock pins. The problem is that by the time they are getting down to where the 1620 is actually located, they are at 0.8 volts.

    kwinn wrote: »
    It would be a good idea to post the object or code you are using.

    With both chips connected to 3.3V and the prop providing the signals pullups should not be required. Read the data sheet carefully though, the software interface is not simple.
  • TappermanTapperman Posts: 319
    edited 2010-11-25 13:21
    TCP71 wrote: »
    I'm starting to think I picked the wrong temperature sensor. I have a DS1620 mounted in a control box down a 10foot run of cable.

    I seriouly doubt you picked the wrong sensor. Try running without the 10' cable, does it run then? There may be a current leak in the cable. Since the DS1620 data sheet says about 10 ua per input pin. Not much load there. And the data sheet states 2.7v to 5v power range.

    Also, be aware, that chip has a stand alone mode. Check your driver.

    ... Tim
  • TCP71TCP71 Posts: 38
    edited 2010-11-25 14:23
    Thanks for all the thoughts.

    My circuit also has two dual FET ICs who's gates are attached to the same lines. I've used this circuit before and never had a problem, but it turns out that both ICs (4 fets) all only allowed the output from the prop IC to get to 1V. I've removed the FETS and all is good. Never seen 4 shorted fets all at once.

    I appreciate the thoughts.
  • TappermanTapperman Posts: 319
    edited 2010-11-25 15:28
    TCP71 wrote: »
    My circuit also has two dual FET ICs who's gates are attached to the same lines. Never seen 4 shorted fets all at once.

    Well ... might be you could seperate the two systems into seperate cables? Should save you loads of grief. Maybe consider driving the FETs with opto couplers actually on the board with the FETs. Then the lines sharing the path with the DS1620 will not cross talk to the FETs. Great CMRR and cheap to ... just doesn't do well at high freqs. (trade-offs)

    Not sure if I understand why you would put the same signal lines to the DS1620 as to the gate lead of the FETs? If I understand correctly what you wrote in your last post.

    Possibly an H arrangement? Motor drive maybe? And detecting the motor temp?

    ... Tim
Sign In or Register to comment.