Modifying the hottop roaster

UNM

I figure this is deserving of its own thread as quite a few people have hottops and there are some tweaks that can improve them, especially the older models.

Mine is the 8828D, but many mods will no doubt be applicable to the other models as the basic design hasn't changed much over the years.
Normal safety warnings apply - not only due to 240 volts, but also high temperatures.

First up, and specific to the D and earlier is manual control of the heater. The trivially easy way is to take the wires from the element, disconnect from the circuit board, and attach a 10am plug.  Given the lag between applying power and heat output changing, switching on and off at the wall can accomplish rudimentary heat control.

I'm going for a slightly more sophisticated method - using a triac control circuit to vary element power. I checked with a power monitor and max heating power is 690W. With the triac, I can vary between 120 and 680W - good enough when an on/off switch is also available.

Next up is insulating the casing - thanks to suggestion from AM, I have a fire blanket that will be cut up and used to wrap the inner casing, with some cut outs for the vents.
I haven't decided whether to leave all vents open, or just the top and the one close to the vent in the external casing. It seems odd to have what is effectively a chaff vent on the other side.


Fan control will follow in good time along with extra thermocouple sensors to measure bean temp and environmental temp. I plan on following Randy Glass's tips on espressomyespresso.com for installing thermocouples.


I'll also investigate making the casing slightly more chaff resistant as it does collect in various nooks and crannies.


Anyone else got interesting and useful mods/tips/tweaks for the hottop?

Intense Coffee

I have a Thermocouple fitted to my Hottop B (by Greg Pullman), which comes std with suitable manual controls, but I am  interested in the blanket insulation, and whether it causes any side effects, and also ways of preventing the chaff from inundating the electronics and fan housing areas. I believe AM has in the past discussed fitting a mesh over the bean chute air intake holes, but not sure what form that takes, so would be interested in seeing any other such mods. You may be able to get upgrade kits to turn the auto models into "B" models through Greg Pullmans outfit. Graham

gregpullman

Beanflying has done / is working on a manual power control mod to his D so you might like to chat with him about it. If you've measured max power at 690W I would recommend a triac that can take more than 680W! Apart from running at max capacity, if your line voltage climbs a few volts your power is likely to tip over 700W. I would be cautious about blocking off vents the manufacturer has gone to the trouble to install. Also be careful when cutting fire blankets as they may have lots of very very very fine fibres which don't go well with lungs, especially when you've got a nice strong fan to stir them up! If you want a neat bean mass probe installation you could use the method we do and drill through the back panel to install the probe. Not trivial and requires disassembly but a lot neater than a cable hanging out of the bean load chute. Greg

beanflying

Good Idea for me to extract something and post some photos of my install and to describe what I have done to mine finally  :-[ Off to Melbourne tomorow and Saturday but will add some stuff early next week. The basics of mine was to leave as much of the old D structure alone and to control just the low power side of the power board. For those that haven't seen inside a Hottop there is 2 main circuit boards the Display one which also houses the brain side of things which then feeds into a single IC on the lower board which in turn powers a series of relays to handle the power to motors elements etc. The only major change I have made to this lower board on mine was to exchange the element relay with an SSR. SSR like with a PID unit on an espresso machine is just a fancy electronic relay without the physical points like the more normal P/Stats and or relays use. In theory much better life and smoother faster switching.

UNM

Greg, yep, already know most of what beanflying (and yoma on the other forum) did for manual control. I am going the triac route for now (my triac can handle 16 amp - 680 watt is just what my power monitor measured with the triac circuit in place). I may change in the future, but for now it is quicker and easier. Good point about thermocouple placement, I had forgotten that option. Will probably use your method. Any idea what colour the element control wire is? I think I should probably disconnect it to avoid unnecessary switching of the relay now the element is not under hottop control.

UNM

Thanks for the wire specs, I also spotted that in Yoma's original post he put pin numbers on one of the images.  Colours are different on mine, but most pins are the same, confirmed pin7 is heater and disconnected at control board. Interestingly, mine only has 7 pins - no interrupt. I have put in limited insulation - opposite side to the heater and from base of drum to just below the air vent. Instead of fire blanket, I used a silicone pot holder from The Reject Shop - they are selling them for $3 and they are 17.5cm square, waffle style about 8mm thick. It is a good fit between inner and outer casing, exactly the right length front to back, easy to cut to size and with the waffle texture, traps air beautifully. I may yet put another section in the opposite side, but this would interfere with airflow from the outside vent which may be a good or bad thing, so will wait until I better understand the somewhat bizarre airflow in the hottop before messing with that.

UNM

I am a very happy chappy  ;D Ran one roast cycle with no beans, all good. Ran once cycle with the partially roasted brand from the time of Frank N Poppers demise. First roast tonight with manual heat control. Decided to use Peru Ceja De Selva as I not only like this bean, but it was the last successful popper roast, so I can easily compare. 16min roast, 12min to FC, pulled 15 sec into SC infinitely better than the original setup that went straight from first to second. One safety concern is that it is all too easy to leave the heating element on accidentally. I may use the main 5v to drive the heater relay and use that as a breaker to ensure the heater is off when the main circuit is off. More mods will surely follow. I really want data logging and auto profile control and have a couple of plans. May have to join up with homeroasters as they have some good threads. For now though, it's enough that I can roast 250 gram manually

UNM

I am now within a hairsbreadth of ordering a TC4 board (to go with the Arduino compatible on order already). Shipping from the US is pretty expensive, relative to cost of board, but two boards would be same cost. Anyone else interested in one of these? Hope it's ok to post links to other fora here - if not, mods please edit accordingly. ref: http://homeroasters.org/php/forum/viewthread.php?thread_id=1774

UNM

Just a brief update. My TC4 board and lcdadapter are on order along with an extra thermocouple. Just after ordering my arduino UNO, fleabay informed me it was a counterfeit and I should request a refund. It arrived and worked ok, but out with the tin snips anyway. I now have an arduino mega on order. For all the extra cost, I figure it was worth it to get more storage and I/O. Programming seems easy so far

UNM

My last post here was deleted, but that's ok, I'm used to it. Anyroad, here is my latest toy. Much work ahead, but so far, so good. And yes, I know the deleted posts were due to technical rather than personal reasons.

admin

on 1316047635:

My last post here was deleted, but that's ok, I'm used to it. And yes, I know the deleted posts were due to technical rather than personal reasons.

yes, apols for that Ewan. A