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Location:
Land of Oz
Registered:
June 2004
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Re: Who can help with building a temp gauge?
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Wed, 04 May 2005 22:44
 
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Hi,
You'll need two 1620 chips - 0ne for the compressor cabinet and one for the room. They communicate to your microcontroller via a 3-wire interface.
The 1620 also has low and high temp threshold outputs. You program the 1620 to specify your lower/upper temp limits. When these limits are met it outputs a signal on the low or upper threshold line. Therefore, it is possible to use the 1620 as a thermostat and, by using its upper/lower output lines it can switch on or off devices as the temp thresholds are met. However, this doesn't provide you with a display.
So, if you want to display the temp then you'll need the microcontroller/LCD setup. Your microcontroller will constantly read the temp registers of the 1620 and display them. I assume that you must have some upper/lower temp limits for your situation? When these limits are met you want the m/c to switch off (or on) the compressor.
Are your temp limits static or do you want to be able to configure the temp thresholds as you desire. If you want static limits then you don't really need a keyboard, if you want to change these limits then you'll need a keypad or a couple of buttons. Do you want a buzzer or some other device to sound an alert that a temp threshold has been exceeded?
You'll need 4 (or is it 5? - I'll have to check) lines minimum to control the LCD, assuming you use a parallel LCD. You can use a serial LCD to reduce the number of lines required, but these are more expensive.
So, basically - assuming static temp thresholds - you'll need 6 lines for the two 1620 chips (3 lines per device) and 4/5 lines for the LCD display. You may be able to get away with less than 6 lines for the two 1620 devices by using some multiplexing, assuming this doesn't upset the 1620 chips.
If you want to turn something on or off, then you'll need a line for each one of these. If you want a manual override to turn things off/on, then you'll need a line for each override button. An audible threshold buzzer would require a line also.
The number of lines required may exceed the number of lines the 16F84 has, so you may have to go to the next level m/c chip - which isn't a big issue.
The 1620 chips can be remote. I don't think there's a lot of loss through Cat-5 and it may be okay. I assume we're not talking about a huge distance involved. You'll need to provide power for the 1620 devices. This can be through the Cat-5 or by a plugpack at each location. If using the plugpack, make sure the earth wire is connected to the m/c to ensure no floating earth and to stop other spurious readings and spikes.
You need to specify what functions you want - ie, audible alert, manual overide, ability to change temp thresholds, relay control to turn comp off/on, etc. Using this info we can then derive the number of lines your m/c will need to have.
Sorry to be so long winded. I just can't help myself.
seeyuzz
river
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| | Subject | Poster | Date |
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Who can help with building a temp gauge?
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clubagreenie | Tue, 03 May 2005 04:55 |
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Re: Who can help with building a temp gauge?
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EnFlaMEd | Tue, 03 May 2005 10:35 |
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Re: Who can help with building a temp gauge?
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ndgcpr | Tue, 03 May 2005 11:50 |
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Re: Who can help with building a temp gauge?
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Toobs | Wed, 04 May 2005 04:34 |
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Re: Who can help with building a temp gauge?
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clubagreenie | Wed, 04 May 2005 09:13 |
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Re: Who can help with building a temp gauge?
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wilbo666 | Wed, 04 May 2005 11:15 |
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Re: Who can help with building a temp gauge?
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Cool1 | Wed, 04 May 2005 10:38 |
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Re: Who can help with building a temp gauge?
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river | Wed, 04 May 2005 11:27 |
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Re: Who can help with building a temp gauge?
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river | Wed, 04 May 2005 11:45 |
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Re: Who can help with building a temp gauge?
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clubagreenie | Wed, 04 May 2005 12:46 |
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Re: Who can help with building a temp gauge?
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river | Wed, 04 May 2005 22:44 |
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Re: Who can help with building a temp gauge?
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ndgcpr | Thu, 05 May 2005 01:49 |
