[time-nuts] Tbolt temperature Control

Thu Aug 27 00:15:57 UTC 2009

Hi,
your problem should be to adjust to physical reality, then you may
be able to control you TBOLT temperature.
I cannot remember the term in a PID equation that accounts for time  
delay.
In fact there is not one! It is the wrong algorithm for controlling  
almost any heater!
It is excellent for driving pens in pen recorders where mass,  
velocity and position
are the terms.
Thermal control must face some nasty delay functions, like Gauss's  
error function.
When the temperature error signal is delayed, as in the TBOLT, your  
best control algorithm
uses the inverse transfer function of the thermal system to predict a  
somewhat tardy response.
An alternative method that works very well is to create an isothermal  
wall around the TBOLT
which is held at constant temperature. I would suggest your light  
bulb and a small
computer fan to create a local tornado of air around the TBOLT and by  
controlling the
air temperature you will control the entire case of the TBOLT. This  
will have much
faster response and may control the case of the OCXO, voltage  
regulators and not
just the temperature sensors.
There, I have had my 2c worth,
cheers, Neville Michie

On 27/08/2009, at 5:56 AM, WarrenS wrote:

>
> This can also be made to work on the TBolt units that have the 1/2  
> deg course Temp sensor.
> The control loop gets a bit trickier, but it can hold the Temp very  
> close at one its course transitions points.
> This would come in handy for those not wanting to change their  
> sensor to the high resolution type.
>
> Another useful feature to add to a completely independent micro  
> controller so that it needs no other inputs is to have its program  
> smart enough to automatically and slowly readjust its set point  
> control Temperature to just above the highest day to day Peak temp  
> it sees. Needs no extra inputs, It just needs to monitor its own  
> PID loop to see if it even comes out of control due to excess temp.
>
> Note you do not have to pass anything thru or output any RS232,  
> just the ONE bit  if the micro is going to control the temp out bit.
> It just needs to pick up the Tbolt output data in parallel and  
> capture the Temp info.
> If the micro is not doing the Temp control then there is no need to  
> have the extra micro.
>
> ws
> ********
>> Don Latham djl at montana.com
>> Wed Aug 26 17:38:21 UTC 2009
>
>> Heck, Warren, I'll put it on the line :-). Use a very simple and  
>> cheap
>> processor such as a Picaxe, pass the rs232 through it to Lady  
>> Heather etc,
>> and capture  the temperature, using it appropriately. Should work  
>> nicely
>> and keeps the temp control local. Even put a little LED on it to  
>> indicate
>> state.
>> Don
> **************
>> TBolt Nuts
>>
>> To keep My TBolt's temperature constant so that the environment has
>> minimal effect on it,
>> I use an aquarium temperature controller (modified to have low  
>> hysteresis)
>> connected to a low wattage light bulb, placed in a box with the  
>> TBolt.
>> It works OK and keeps the TBolt's temperature constant to well  
>> under 1
>> deg.
>> To do it better and make it  more hi tech,
>> I'd like to have the temperature control based on the TBolt's  
>> internal
>> sensor.
>>
>> What I have found works well is to use the TBolt's own RS232  
>> temperature
>> sensor output data,
>> and with a modified PID type of S/W controller, turn an external  
>> heater
>> &/or cooler on off.
>>
>> The heater can be an appropriate power resistor or transistor  
>> dissipating
>> up to about 4 Watt,
>> mounted to the TBolt case. What I use to cool the Tbolt up to 5  
>> deg C, is
>> a small fan blowing
>> at a heatsink mounted on the top of the TBolt's case.
>> Turning the fan on & off with a S/W driven switch, can be used to  
>> keep the
>> TBolt's
>> internal temperature very constant over a limited external  
>> temperature
>> range.
>> A standard PC chip fan & heatsink may be OK, if it does not add Phase
>> noise due to it's vibration.
>>
>> Because of the long time constant and slow response of the internal
>> temperature sensor,
>> a single digital on-off bit, updated at a max rate of once per second
>> works great for control,
>> No analog needed. To keep the hardware and interface circuit simple,
>> I'd like to be able to use one of the unused standard RS232 outputs,
>> such as RTS, CTS, DSR, DTR  as the heater/cooler control bit(s).
>> This is no problem when doing this in a DOS program or from an added
>> microprocessor
>> that monitors the Tbolt's  communications,  But the question is,
>> can it be done in Windows in such a way that a modified existing  
>> program
>> such as
>> Lady Heather or Tbolt monitor could control an already existing  
>> readily
>> available digital bit?
>>
>> Being a control person, Doing a software algorithm is the easy part.
>> Making Windows do any kind of non standard I/O control, is way  
>> above my
>> capability.
>> I'd like to get feedback from a Windows expert if there is a  
>> simple way to
>> control an existing Digital bit
>> that would be available on a PC being used in a typical setup that  
>> is used
>> to monitor the Tbolt.
>> One way I have heard suggested is to use the sound card output,
>> but I'd like to keep it even simpler than that, Any suggestions?
>>
>> If anyone is interested in developing a program to make an  
>> existing stand
>> alone micro
>> or basic stamp to include this function they can contact me off  
>> line for
>> some sugestions.
>>
>> Thanks,
>> ws
>> ******************
>
>
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