popeye wrote:I see not many adventurous people are out there. I'm willing to sacrifice the behmor. Burn it out, burn it down, whatever. Not that it's not a great roaster (and i would probably replace it) - it's just that I want more consistent and better roasts.

Hi popeye,

I can tell you about some of the mods I've made and give you an idea of what's possible but, as Ira correctly points out, if you're not comfortable with electrical work and to a smaller extent electronics, the mods I describe probably aren't worth the hassle/potential safety issues.

A few months back, I set out to: (1) put the Behmor's heating element under manual control; (2) add an environment probe (I tried adding a mass probe but that effort was unsuccessful); and (3) interface the probe and a heater relay switch to a PC, where I could control/monitor the roast through a program I wrote for that purpose. There are two heat control modes: a software PID and a time proportion-based power setting (5% granularity, 10 second cycle seems to work best). Initially, I almost exclusively used the PID mode but more recently, I've switched over to the power mode as I've found that a 'smooth, up and to the right' heat app curve seems to produce a more consistent and better tasting cup in general for the beans I typically roast (<insert ymmv disclaimer here>).

This effort has been largely successful and I do have a degree of control that I didn't have before the mods. That said, the list of hacks required to accomplish it is longer than I originally anticipated and the end result is still inferior to the control/monitoring potential of, say, the Hottop B (albeit at twice the cost). If you're interested in pursuing this route, let me know and I'd be glad to share the specifics of my experience.

Regards,
John

Hi, John

Glad to see that there's another modder out there. Mine's a pretty simple mod, I have manual control over the heating elements and a digital thermometer that I use sort of like a "tach" to tell me when it's time to bring the heat back on-line via the temperature drop. Lots of interesting things to be done with a B1600 with manual shifting. My general method is to leave the heat on until the start of 1C and turn it off to coast through first crack or until the digital thermometer says I've dropped 10 degrees. On 2C I generally let it heat for 10-20 seconds and then kill the heat for the duration. Very nice FC to FC+ roasts.

Roger

I did a couple behmor mods before loaning it out to a friend. Added a bean temp probe and faster 50rpm drum motor. For BT I made a new drum hub slightly larger than the original so I could drill it out to fit a thermocouple probe. I used a piece of teflon tube in the new hub for smooth operation. I made 2 bean feed troughs that keep a constant flow of beans around the probe tip. To remove drum I just pull the probe out. Had planned on turning the heat control to manual but haven't got to it.

ira wrote:Probably the best way to do that would be to add a couple of switches and a couple of pots to allow you to alter the temperature the control board sees. It's a relatively simple task, but I don't really want to post that info in public as the potential risk(fire) if done wrong is a bit high.

Feel free to contact me off list and if you're not comfortable with messing with wires, I'm just a couple of hour drive from you. My contact info is on the BehmorThing site.

Ira

Last summer when I was playing with a pre-release 1st production run Behmor I split the heater circuit out wired through a toggle switch. This allowed me to run the heater full variac control with rest of the Behmor getting normal line voltage so not slowing or speeding up drum or fans or affecting the electronics. The toggle switch allowed running with full variac heater control or stock. Never got around to splitting out the after-burner circuit or replacing drum motor with higher rpm or figuring out bean temp monitoring method, acquired a CCR HotTop and basically abandoned the Behmor...

farmroast wrote:I made 2 bean feed troughs that keep a constant flow of beans around the probe tip.

Wow, that's an interesting approach! Does it consistently keep enough mass around the tip to have confidence in the readings? It certainly solves the problem of getting a curved probe in and out of the chamber. Btw, now is a good time to point out that I've been an admirer of your ingenuity ever since I came across your roaster a few months ago... you seem to have a knack for coming up with and implementing (something I struggle with, since I'm about as mechanically inclined as a turnip) simple but novel solutions to common problems. Bravo sir.

The Behmor mods mentioned for temperature monitoring, voltage regulation and control of the heater are why I'll be purchasing a HotTop in the very near future.

I hope that second or third generation Behmors take all these requirements into consideration and produce a reliable unit at an affordable cost but for now my mind is made up.

I hear what you're saying. To be fair, though, the Behmor isn't targeted at the manual control/monitor crowd. When I was researching first roaster options a year ago, I wasn't sure that I'd still be interested in roasting six months down the road. The Behmor was an easy choice then and I think it still is for anyone in a similar situation - it's easy to use, beginner-friendly, inexpensive and it's still the only off-the-shelf 1lb (ok, 14oz) roaster in it's price range. Manual control/monitor nerds (and I include myself in this group) are likely better served by a homebuilt or something like a Hottop that's relatively mod-friendly (or making the leap to the $4000+ range for a commercial rig). On a more personal level, the "CCR Behmor project" has accelerated my roaster learning curve while combining three of my favorite things: tinkering, writing software and drinking coffee.

I think a totally pimped out Behmor could produce an exceptional roast. I liked the effect of it's heat application to hard centrals.

Ha! I don't know why but the phrase "totally pimped out Behmor" tickles me for some reason... however, it occurs to me that this seems to be the right thread to pool our collective experiences/knowledge and come up with <Sunday! Sunday! Sunday! Monster truck rally announcer guy>The Ultimate, ok, ONLY Guide To Pimping Your Behmor </Sunday! Sunday! Sunday! Monster truck rally announcer guy>. Here, I'll kick it off with the hopes that others will jump in and share their observations, thoughts, ideas, etc...

Temperature Monitoring

It's easy enough to get a probe in the roast chamber to measure environment temperature. The real question here is: "What's the best location to place the probe?" It's tough to answer that question in a general way so let's make the simplifying and reasonable assumption that the measurements will be used as input to the heat control process (which may simply be a human hand turning a variac knob). This implies that a good probe location would be one that experiences the same or similar heat as the beans and will respond as quickly as possible to heat application changes.

The next question that comes up is: "In the airflow path or not?" It seems to be conventional wisdom that an environment probe should be located outside the airflow path in a drum roaster... although I'm not sure the Behmor qualifies as a "drum roaster" with respect to this particular guidance. The airflow path in the Behmor consists of air flowing from two inlets - the big flap in the back and the smaller opening above the top heat element - and out through the exhaust opening in the chamber ceiling when the draw fan is energized. If we want to stay out of the airflow path, that basically means placing the probe away from the inlet and exhaust openings.

A location that seems to meet both criteria is the space between the bottom heat element and the area of the drum where beans gather when it's rotating, about 1" away from the chamber wall (near the location of the stock temp sensor). The heat shield on the back wall comes in handy if you want to wrap a TC wire around the bottom rung a couple times and bend it such that the tip sticks out as close to the drum as possible without touching it (I have a picture of this somewhere, I'll post it later if I remember).

Getting a probe into the bean mass is a bit more tricky due to the completely enclosed drum. It can be done if you have the skills, however, as JohnMoody (https://www.coffeegeek.com/forums/coffe ... ast/333876) and farmroast have ably demonstrated.

Heat Control

This is the part where we wrestle the Behmor's control and safety features to the ground, acknowledge that equipment and personnel damage may result from doing so and we agree to hold poor TahoeJoe faultless since we took it upon ourselves to hack his nice, well-mannered, consumer-friendly device. If, by adding environment/bean mass probes, we merely voided the warranty, controlling heat application in the Behmor requires voiding the hell out of the warranty.

Actually, it's not quite that bad but there are aspects of the Behmor's control logic that need to be considered. We start with the assumption that heat is the only thing we want to control... I start with this seemingly basic assumption to distinguish the simpler heat control mod from the larger, more encompassing mod where we disable the stock control logic altogether and put everything under manual control - the heater, the drum motor, the cooling fan, the draw fan, the main cooling fan, the afterburner heater, etc.

There are basically two approaches here and the one you select depends to some degree on how you plan to drive the heat control: variac and switched. A nice hybrid variation on this is the one mike points out a few posts back.

For variac control, it's best to split the heating elements from the Behmor's circuitry and power it exclusively through the variac. As others like drdna have pointed out, powering the digital control circuitry with a variac isn't particularly good for the gear nor beneficial in any way. Disconnecting the elements isn't difficult, as quick slide connectors are common on the Behmor's control board.

For switched control, you can either split the heating elements out and power them separately like we did for the variac or keep them in the existing circuit. In either case, we insert a toggle switch or relay in the supply circuit, allowing on/off control of the heating elements.

A description of the stock heat application logic is in order at this point so we can make an intelligent decision as to the degree of heat control we'd like to have (no pun intended). Internally, heat is switched on/off via a mechanical contact relay on the control board. On P1 (full power), the stock logic cycles the heat off at 400f and back on when the temp, as measured by the stock sensor in the chamber wall, drops to 360f. The draw fan seems to be activated at +7:30 and stays on for the remainder of the roast. It's been a while since I dealt with the stock logic and I don't have my [few] notes handy, so I can't recall if the 7:30 is a fixed time or a percentage of the total time. Also, IIRC, the other profiles simply use a lower cycle-off temp, while the cycle-on temp is 360f regardless of profile.

First, the simple approach. By leaving the heating elements in the existing control loop (note that this limits you to switched control), you effectively have partial control over the heat application, or modulated control if you like. Let's say, for example, that you're perfectly happy with the default heat application pattern and all you *really* want is a way to kill the heat at certain times... say, to control a particular phase of the roast. If this is the case, partial control is all you need. Note that this approach precludes the ability to turn the heat on when the default logic has turned it off (technically that's not 100% accurate but it is in the simple approach).

Now, the more involved full control approach. If you're using a variac or you want to be able to profile or you have some other use case that makes partial control undesirable, the first thing you should do is liberate the Behmor from it's stock temp sensor. In addition to feeding the heat control loop, the control logic uses the sensor to detect an overheat condition (which, IIRC, is ~410f) and a too-hot-to-start condition (which, IIRC, is ~175f). It'd be great if you could simply unplug the molex connector for the temp sensor from the control board, but alas, the Behmor won't start if it doesn't detect the sensor. The easiest solution is to move the sensor from the chamber wall to outside the roaster so it always measures room temp, effectively disabling it. Taking the stock sensor out of the picture has done a couple things for us. First, it prevents the control logic from shutting down the roaster at an inopportune time. Second, it allows us to preheat the chamber before putting the beans in (something that's normally difficult to do given the too-hot-to-start check). And third (ok, a few things), we can stick a switch/relay in the existing heat circuit and - unlike the partial control arrangement and so long as we always use P1 - have full control over the heat since P1 profile+room temp sensor=heat power is always on as far as the control logic is concerned.

Great, so now we have full control over the heat right? Eh, not completely. The draw fan is still being controlled by the stock logic, which means it will dutifully cycle on at seven and half minutes into the roast and *KERCHUNK* there goes that nice smooth heat curve you've been working on thanks to the sudden 20 degree drop in ET. Is that really such a big deal considering that the default heat application logic regularly causes 40 degree drops? I'd have to defer to someone with superior roast/flavor chemistry knowledge (virtually anyone here I would imagine) to answer that question with any kind of technical accuracy. However, I would have to assume that if you've gone through the trouble of placing the heater under manual control, not having manual control of the draw control as well would be irksome to say the least. Fortunately, splitting the draw fan off and putting it on a switch is trivial since it's an AC fan. Speed control is also an option here, although I've had limited success with the only fan speed switch that I had handy at the time that I was fiddling with it.

Ok, I think that covers the basics from my admittedly limited perspective. Hopefully there's something of value here as a starting point and others will add to it.

Nice thread.
Couldn't help but thinking, there's a good project going on over at coffeetime uk
http://www.phpbber.com/phpbb/portal.php ... etimeboard

and a more detailed discussion on the wiki http://coffeetime.wikidot.com/gene-cafe ... od-stage-1

on attaching a dimmer switch (as in a lighting dimmer) to control heat output on a Gene Cafe, rather than having a huge variac laying around each time you roast.

Was thinking this might be applicable to modding the Behmor and getting direct adjustable control over the heating elements.