Soldered both kits together with no real problems and both appeared to work ok. After about 8 hours working the temperature read out stopped reading and only reads --°F. Left everything powered down for a while and started working again, then same problem. The problem seemed to get worse and worse and now it only reads --°F. Also, checked sensor wiring and removed and re-soldered the sensor directly to PCB. Again worked for a while and then stopped. It should also be noted that when starting to fail, every 2nd display of the temperature would read ok, before constantly reading with the two dashes.
When it was working the span accuracy I found to be dubious. Calibrated at 68° against a certified thermometer, when the sensor was put outside for over half an hour, it read a good 10 degrees above the correct temp. Here in the UK its been pretty cold and the outside temp was around 28° and the sensor read 39°. Any ideas? Thanks
Is the clock working fine?
If you measure at the sensor connector, do you get a stable DC reading (measure between GND and IN)?
Do not extend the sensor from the sensor-PCB.
What is the distance between sensor-PCB and K8089 board?
Make sure that the sensor-PCB does not get damp or wet.
Sorry, this forum does not allow picture uploads
If you can provide LINKS (e.g. by using a free online picture base) to HI-RES and SHARP pics of your assembly (both solder- and component side)
then we can take a look and provide some feedback.
[quote=“VEL417”]Is the clock working fine?
If you measure at the sensor connector, do you get a stable DC reading (measure between GND and IN)?
Do not extend the sensor from the sensor-PCB.
What is the distance between sensor-PCB and K8089 board?
Make sure that the sensor-PCB does not get damp or wet.
Sorry, this forum does not allow picture uploads
If you can provide LINKS (e.g. by using a free online picture base) to HI-RES and SHARP pics of your assembly (both solder- and component side)
then we can take a look and provide some feedback.[/quote]
Hi. Thanks for the help. I’ve renewed the sensor on the PCB (the LM335Z) and so far (about an hour), the temperature has behaved itself, giving a steady reading. Unfortunately I don’t have a multimeter at hand. The length of the cable between the K8089 and the K8067 is about 8ft. I assumed the length of this isnt too much of an issue as its in loop. I’ve also ensured the sensor goes straight into the PCB. Perhaps I damaged the sensor or it was just faulty.
I want to connect two K8067’s to the K8089 through a switch. I need the switch to be operated by a relay. I’m figuring I’m going to need something that gives a pulse of intermittent output. I’m wanting the clock to display inside and outside temperatures, rotating between the two K8067’s on each temperature display cycle. Any ideas? Do Velleman do anything that would be suitable? Thanks
You could use something like an MK188, however, there will be some issues:
- You will not know which sensor is displayed, unless you add e.g. an led that indicates that the outdoor sensor is active.
- The switching will most likely cause undesired behaviour of the display. The K8089 samples the sensor input at regular intervals in the ms range.
If the relay is switching when sampling occurs, a wrong value or even ‘–°C’ can be displayed. - The external timer will loose sync, so there is no guarantee that the sampling will occur at the right time.
[quote=“VEL417”]You could use something like an MK188, however, there will be some issues:
- You will not know which sensor is displayed, unless you add e.g. an led that indicates that the outdoor sensor is active.
- The switching will most likely cause undesired behaviour of the display. The K8089 samples the sensor input at regular intervals in the ms range.
If the relay is switching when sampling occurs, a wrong value or even ‘–°C’ can be displayed. - The external timer will loose sync, so there is no guarantee that the sampling will occur at the right time.[/quote]
Thanks for the advice. During summer months I suppose that could be a problem as the outside and inside temps could be fairly close to each other. I have got the MK111 which I used to drive a slave clock with 30sec pulses, however I found it to drift quite quickly and not accurate enough to keep steady time. Is there any way of slowing down the interval between the time and the temperature, what determines this? If this could be reduced to just show the temp every minute, then set up the relay to change over in between the minute, it should stay away from the switching at the wrong time, at least reduce the likelihood. Thanks
Unfortunately, the switching time is determined and fixed in the firmware, so it cannot be changed.
No worries, it is certainly something to think about though. Looks like that was a faulty sensor, working perfectly now and checked through a range of temperatures. Thanks for your help.