UNO ELECTRONIC HEATER & THERMOSTAT (1994 Update)
By Neil Souch (Area 22) & Bill Reid (Area 20).
An article in Area 22 Local Newsletter by member, Neil Souch suggested an update on the use of the extremely capable Uno Heater and thermostat, from the original published in CRCN No. 28, January 1983. :-
The Uno was designed mainly as a fish tank heater and in use I found the heater element and the temperature control probe tended to float about in the temperature bath. As there is no facility to anchor these items down (the heater element requires a minimum of 3" of water above it) I had to make up two suitably shaped pieces of flattened lead to keep them located correctly in the bath. Just simple flat `U` shaped pieces were made and these did the job admirably. I used a small oblong shaped plastic storage box for the tempering bath container. Filled with about 4.5 Litres of water it provides a depth of 3.5" (just right for my Dev. tank). Initial tests showed that the UNO heater was having to work flat out on it`s full setting, in order to maintain 38C.
I was not impressed with this as there was no adjustment left to give a temp. boost for the winter if the bath temp. started to drop. I decided to insulate the water bath and made up a close fitting outer box for the plastic box to sit in. I used some replaceable small profile plastic bubble wrap. Providing this crude insulation did the trick and I was able to immediately back off the UNO`s control switch to gain the necessary reserve power output. The combination of the UNO and my insulated box provides a very stable bath. When I know what sized solution containers I shall use I`ll probably make a removable lid with appropriately sized tank and container removal holes to minimise heat escaping off the surface of the water. So, I now think I`ve cracked the tempering problem and the next move is a few more trial runs with the set up and then on to having a go with some actual films!
T H E U P D A T E......
With no moving parts involved this should make it very reliable. The thermostat must`nt be immersed and is sealed against tampering which would make it`s two year guarantee null & avoid. It has a 500watt, maximum output and a temperature differential of +/- ¬C. as against +/- 2C. of most bimetal thermostats. There is no need to add a second heater until 30 gallons of water is used, which means that the 200watt one supplied should cover anything that is required for home processing.
The thermostat is fixed to the side of the water bath by two stainless steel clips which are treated against salt and toxic chemicals. The bottom end of the clips are doubled over to fit over the edge of the bath. (It was planned to use rubber suckers at a later date, and this may be so in Brian`s case).
The heater cable (white) and the Probe cable (black) come out at the top of the thermostat with convenient length. The heater element is contained and sealed inside a, black pained, aluminium tube and a bracket with two plastic spring clips, which also has two suckers, which stick the whole thing to the side of the water bath. With the sucker removed the cable could be screwed to the side for a more permanent water bath set up.
The Probe sensor is contained, and sealed, inside a green plastic capsul. A `sucker` is fitted to the cable so that it can be moved along and fixed at a convenient place, as far away from the heater element as possible. (I found that by `strategically` placing the `sucker` at the right hight and distance from the thermostat Probe, you can get the the probe and cable to lie, on the bottom, without the need for any weights). There is no method for water circulation, but UNO recommend using a fish-tank air pump.
The mains cable (white) also with plenty of length, comes out at the bottom of the thermostat and is the standard three-wired cable, for use with a 3amp, fused plug and should be earthed. The thermostat is T.V. suppressed with a re-enforced insulation and has a temperature range from 10C. - 48C. (50F. - 120F.).
On the face of the thermostat are the working indications. A `red` L.E.D. glows when the mains is switched on, and a `green` Neon, is extinguished when the heater should be working. On the top right-hand side is the Temperature Control, which is a black plastic knob that can be removed once the desired setting is found, but you will have to covert the opening with a piece of tape to stop liquid, or dirt, getting into the electronics. The knob turns an indicator seen through a long narrow window and a plus/minus mark shows which direction will raise or lower the temperature. There is no temperature numbers and this has to be found by using your own thermometer.
Precise Temperature Control (test)
With the bath filled with water at 38C. and the thermostat switched on I checked for myself the claim of plus/minus ¬C. control. As soon as the thermostat switched off I then watched the drop in temperature on my thermometer until the thermostat switched in again. Over a period of an hour I found that the temperature dropped to nearer «C. however, allowing for the variations between many thermometers I was satisfied that the tollerance was well inside the «c. which is usual allowance for E-6 processing. If you want you could step up the temperature to 38«c. and the temperature shouldn`t drop any lower than 37 & 3/4C. which is all you can really expect and well within working range.
Dry Test Run.
For a dry test run I set up the thermostat and heater in a plastic washing up basin. I filled the basin with water at around 40C. and then the Dev. tank and six bottles and placed them into the bath, then switched on the mains. The L.E.D. came on and then it was a matter of turning the temperature control knob until the `green` neon went out, and check the temperature with the thermometer to find the correct setting for 38C. This took about half and hour or so, checking the temperature of the bath, bottles and tank to see if there was any change. I used my Patterson chemical mixer to agitatethe water every so often. Inside the hour I could have started processing had I any film in the tank.
Processing Run.
A little while later I had enough films exposed to start some `real` processing. In the meantime I had come across a secondhand `fish-tank` air pump, at a Reading Flea Market and set this up for water circulation. The outlet was placed alongside the Probe so that the water moves moved over the probe. If you don`t have an air pump you can simply agitate the water every now and again with some sort of paddle.
With six (600ml) bottles placed in the basin I then filled the basin with water at 38C. and switched on the UNO thermostat. When the bottles reached 38C. I placed the Developing tank, which had two films in it, into the water bath and placed a weight on top to stop it floating. Again, within half and hour everything had settled at 38C. and processing could begin. Just before starting I filled two 1Litre sized jugs with water at 40C in preparation for the first two minute wash right after the 1st. development. I then began processing, with the thermostat easily doing it`s job and the air pump circulating the water without my having to watch either, while keeping my eye on the timer and agitation stages. The results were fine with the bottom film being perfectly processed. However, I had a green cast problem with the top film which had nothing to do with the thermostat and which I discovered later was due to some carry-over from using the `twiddle` stick agitator. (Ever since then I have always used "Inversion Agitation" exept for the first `15 sec. agitation when first placing films in the tank).
Conclusion. (Update).
In spite of nearly `eleven` years having past since first using my UNO Electronic Thermostat, it is still giving excellent service and hasn`t let me down at any time and I can thoroughly recommend this very useful item. My only criticism would be of the `fiddely` temperature control knob, and the lack of any `guage`. However, as I say, it works perfectly, with only a slight `tweeking` for the winter months. The only form of insulation I use is, a sheet of thin `polystyrene`, from packaging, which I stand the basin on, to stop heat being lost through the bench-top. However, Neil`s suggestion of using bubble-plastic, is an excellent one, and perhaps I could suggest adding a sheet of `aluminium` kitchen foil to give added insulation.
I have never experienced Neil`s problem of having the control used at full setting and wonder if this might be due to the amount of water he is using in his water bath! The setting on my model is well down from the top mark. With 200watts you should be able to boil a kettle with it, or keep it just on/below the boil.
Area 9 member, The Rev`d Ronald Hatfull, also expressed some concern over the UNO as regards it`s +/- claim! and that he found at least `1C.` drop between it cutting off and back on again. However, as I say, I have never found anything to give me any concern over this and the UNO Electronic Thermostatic heater remains a firm favourite and I have used it for both 300ml & 600ml sizes of bottles.
Les Tovey (Area 22) also writes:-
I read with interest the article in the July 1994 issue from Neil Souch re the UNO heater and his tempering bath. He is certainly thinking along the right lines. My UNO heater was purchased many years ago and is still in good working order. With regard to keeping the heater and sensor in place, I received with my kit three sucker pads, two for the heater and one for the sensor, although I must admit I had to stick them down with adhesive and no trouble since.
Perhaps, if I explain my own method of processing with E6 it would be of some help to members. First of all let me say I have been mixing my own brew since the days of our old friend Fred Harvey, but when high temperature E6 came along I had to think again.
I purchased a plastic container about 4" deep, made up a box from pieces of chipboard, lined it with 1" polystyrene and dropped the plastic containers in. Also a top was made to completely cove the container, again insulated with 1" polystyrene. Now, here comes the tricky bit. I used six 2lb. jam jars, with the necks removed, for the various solutions. How to remove the neck of the jar? Fill jar with cold water, to where you want it to break, then about ten turns of garden twine soaked in methylated are wrapped around jar about 1/8 of an inch below water line. Put a match to it, and in two minutes it's done, a clean break. The next job is to cut holes in your tempering tank lid to receive the jars and fit your UNO in bath, (heater and sensor should be as far apart as possible within the tank). There is just one other thing that I consider very important. I fitted an old gramophone motor with paddle to circulate the water.
As you can appreciate with this system there is no pouring from bottles, no contamination from funnels etc. but spot on processing and the time taken to remove spiral from one jar to the next is only seconds. Agitation is achieved by gently lifting spiral up and down within the jar. Washing is done in a similar way, but this time I drop the film into my film processing tank, fill with water, plunge up and down rather vigorously for 30 secs, then empty, and so on.
Oh! I almost forgot, I used tops from coleslaw or yogurt containers to cover jars.
"The Uno Electronic Thermostat & Heater is made by Uno Products Ltd, Uno House, Arnold Street, Nantwich, CW5 5BR. And, is available from your local JESSOP photographic shop".