Servo driver?

[Tim_Duggan]

Tim, the mechanical thermostat only weighs about a 1/4 of an oz and is small enough to fit in just about any boat. It is as quick as a servos response time, quick enough to control the cylinder head temps all around the course. When I complete my dyno, I will finish the developement of the thermostat. Just too many projects in the works.

Charles

Charles,

Do you have an approximate ETA on these? No pressure - the reason I ask is that I'm at the radio rigging stage in my new 21 rigger right now and could save myself some work if you aren't far off..

 

[dwilfong]

Tim the sensors used on my Eagle tree are a very small thermal resistor. you can use this with the 555 driver circuit shown in a earlier post to control the servo. would also use the pot that is shown to get the centering and end play right.

this would be a proportional function to the servo.

I know you want a on off set up but this might work out good.

David

 

[Tim_Duggan]

Tim the Perry valve will go from completely closed to completely open in less than half a revolution. and yes it dose close off completely.

It has a v cut orifice on a tube to do this kinda like a K&B carb spray bar.

David

I threw the last perry valve I had in the pond about 10 years ago after it gave me grief...... not the nicest valves to use on small engines. What does it flow at at 90 degrees from closed - will that be enough?

 

[Greg Moss]

Hi Tim

The auto reset thermal switches in this style come in NO, NC and changeover versions and a wide range of temperature set points. Someone like RS Components at least has data on their whole range, but they're available from a lot of suppliers. This will be somewhere to start, at least to see if you think they're useful.

http://australia.rs-online.com/web/c/automation-control-gear/industrial-switches/thermostats/?searchTerm=switch&sort-by=default&sort-order=default&view-type=List

Cheers

 

[dwilfong]

Tim 45 on the BM meter at wide open and 1/4 of a turn to closed.

I found that the water flow equals the fuel flow on the .21 in my testing.

I was going to hook the valve right on top of a small servo. Direct drive no slop and real small package.

David

 

[Tim_Duggan]

Tim 45 on the BM meter at wide open and 1/4 of a turn to closed.

I found that the water flow equals the fuel flow on the .21 in my testing.

I was going to hook the valve right on top of a small servo. Direct drive no slop and real small package.

David

Now THAT is a great idea. Would you put it in your main radio compartment though?

Greg,

Was thinking the RS switches are too big (shame really as I have an account there). Found this though http://www.devale.com/probe-thermostat/1300-probe-immersion-thermostats.html

 

[Charles Perdue]

Tim, the mechanical thermostat only weighs about a 1/4 of an oz and is small enough to fit in just about any boat. It is as quick as a servos response time, quick enough to control the cylinder head temps all around the course. When I complete my dyno, I will finish the developement of the thermostat. Just too many projects in the works.

Charles

Charles,

Do you have an approximate ETA on these? No pressure - the reason I ask is that I'm at the radio rigging stage in my new 21 rigger right now and could save myself some work if you aren't far off..

Tim, I do not have an ETA at this time. The dyno is my #1 toy project and I will need it to finish the thermostats. I only get to work on my toy projects during the cool months when I cannot work outside. I am trying to wrap up some of my outdoor projects also. That is why I had to take a year off on making the Zoom carbs.

 

[dwilfong]

Ya gust hard plum it in and out with a small piece of tube at the valve for the connections.

My .21 rigger is in time out right now. I named it after my X.

David

 

[Greg Moss]

Tim,

those devale switches would work and have a wide variety of actions available. Mounting and ensuring thermal transfer would be easy enough. They're very similar to what we use here for sensing in very nasty chemical tanks.

The other types are big for sure, but depending on airflow they could be attached to a flat head like an Orlic for example, but would probably be better in a mono.

In either case, the snap action makes them useful and they both have a range of hysteresis parameters available.

 

[Tim_Duggan]

Tim, I do not have an ETA at this time. The dyno is my #1 toy project and I will need it to finish the thermostats. I only get to work on my toy projects during the warm months when I cannot work outside. I am trying to wrap up some of my outdoor projects also. That is why I had to take a year off on making the Zoom carbs.

No problem Charles, Thanks for your contributions!

 

[Tim_Duggan]

I just spent a little time in the workshop with my 4PKS & 614FF receiver, a Hitec HS50 and my 21 rigger. I've worked out how to make the HS50 work on CH4 assigned to the push button on the handle grip and to act as a 2 position setting. So I can rig everything required up hardware wise and test it manually. To automate it further down the track I'd just need to unplug the servo from the receiver, and plug it into the control device.

Next up I need to get a suitable valve. The Perry inflight looks to be the lightest and most suitable to go from completely closed to sufficiently open for a 21 in 90 degrees of sweep. Anyone know if a HS50 is strong enough to move the Perry valve?

 

[Tim_Duggan]

Thanks Greg,

I might even have a fuel doctor somewhere in my junk pile.....

 

[hugh hargett]

Tim the sensors used on my Eagle tree are a very small thermal resistor. you can use this with the 555 driver circuit shown in a earlier post to control the servo. would also use the pot that is shown to get the centering and end play right.

this would be a proportional function to the servo.

I know you want a on off set up but this might work out good.

David

david he can replace the pot with a servo pot with a toggle a two resistors that have the value of the pots endpoints. it will open all the way one way and all the way the other. If you wnat to control the endpoints try one of the schematics above with the trimmer pots as well as the main pot the trimmers would be to set the endpoints and center lilkely.Ill post some code in a minute for a microcontroller based servo driver .

thermistors will work fine on the temps but you need to set the reference voltage with another resistor creating a voltage divider the wire it to that node of the circuit . to make it better you can impliment a few op amps and put in a schmit trigger to so you can create a dead band - a range of minute changes it will ignore . you will need a comparator or opamp to impliment the hysterisis (fancy word for feedback) in an analog circuit. with the mcu based circuit feed back can be accomplish through code and on of the general i/o's

Hugh

 

[dwilfong]

Hugh the circuit in post 32 if you replace R1 with the thermal resistor you can move the servo with the temp change. you may have to add a resistor to the circuit to keep the values in line. then you can use the pot for centering the servo and adjust the end points.

Keep it simple don't have to take it to the max on design.

David

 

[hugh hargett]

AWW David, opamps, comparators,schmit triggers,feedback, it all sounds lofty, but they are just simple general purpose ic's. Its really not that bad yall. Seriously. Ill "build" one of these circuits today. David ill get you some info to look at too.

 

[hugh hargett]

Tim heres an example of a mcu based servo controller-the audruino board is very similar to this one.







the end points and speed are set in the code.

to do a pot based controller youd impliment a rc decay circuit and code it to poll the rc circuit where the pot is the "R" in the circuit.

my board is a project board but you can get the stamp in a similar form factor as the nano audruino unit. Theres no preference here this is just what i already have. I set this up almost a year ago no one ever payed attention i was told I was in "star trek" mode once again . This was the circuit to controll my canard I was goint to 2 photo shudders replace the buttons and put the shudder on the rudder arm so in and out of the turns the flaps would adjust . Then i would finish it with a 3 axis sensor teach it what a level ride attitude is and do all it can to keep that attitude as well as full flapup if it saw a degree indicating and imminent blow over. They blew it off <_< .IF folks start listening instead of doubting so much maybe I can help a little -_- .

http://www.parallax.com/Store/Microcontrollers/BASICStampModules/tabid/134/ProductID/9/List/1/Default.aspx?SortField=UnitCost,ProductName Yes it cost more but im already familiar with the language thats how most choose, they go with the chip that has a code they are familiar with,but its fairly easy to learn new ones. You just need to know the syntax; which comes with the data sheet for the chip

hugh

 

[hugh hargett]

the difference between the audruino and basic stamp is the first is based around an atmel chip the bs2 is based around a pic chip thats all

 

[hugh hargett]

David you need to mount a two wire o2 sensor on your pipe or we need to find something suitable to measure everything. if you want lambda control of your 3rd needle the best thing to do is forget SWAG we can simply calculate stoimetric efficiency based on chambersize intake air period.If there is no math involved you will be stabbing at the dark . Lets go on a calculate what should be the optimum mix based on carb cfm and combustion chamber and fuel power factor. ill look up some formulas and glance at that audruino code syntax.

Hugh

i told ya i had your back

for my active canard project I was going to mount these in the sposon trailing edges : http://www.parallax....84/Default.aspx

thinking more on it we can just use the eagle tree sensor or get another one if you will still have the eagle tree on board

 

[Jim Caldwell]

Hugh, Build it and they will come!

 

[hugh hargett]

4 builds goin right now JIM -_-

1 dumas 20

2 prather 40

3 90 jae

4 PTss45

plus

5 atlas rework

6 u25 lsh pak

7 1/8 circus nitro conversion

8 MRP tunnel rebuild

9 Race Clock

Its all on the bench

Thats quite enough building brother. Anyone that needs to see more just wants to see another boat built

Building for others requires money $$$$$$$$$$$$$$$$$$$$$$$$ doubting me will cost you double