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HVAC servo

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tvrgeek Avatar
tvrgeek Scott S
Hillsborough, North Carolinia, USA   USA
1965 MG MGB
OK electric servo for the heater valve is easy. I figure one could get a second one and take off the valve, put a crank on it and do the flap door.
But, how do vacuum servos work? I can see on/off, but how to they work porportunatlly? Or do they. I found nothing on Google. Maybe cheaper using breaker yard parts.

Is there any advantage of using a 4-port heater valve in the MG?

Does the Mini head take off port block bolt up to the B series block? Easier than modifying a Smiths valve.



Cogito ergo sum periculoso

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lokiufgator Avatar
lokiufgator Gold Member Mike S
Evington, VA, USA   USA
I'm currently building my own around an Adafruit Trinket.
https://www.adafruit.com/product/3500
I tried a regular 10k rotary potentiometer but didn't like the fine motor control it had in either linear or logarithmic scales.
Instead I'm currently working on both a slider style potentiometer which has almost the full 90 degree range of motion I want:
https://www.sparkfun.com/products/9119
But I'm also playing with a 10position rotary switch where I can solder in a range of resistors to get a near perfect movement of the flap doors however I like them to be, but it'll have 10 distinct detents instead of the slide which could move from bumps and such.
https://www.sparkfun.com/products/13253

And it's all to control this servo which will be connected to the flapper by an RC bar with ball and socket joints on both ends:
https://www.adafruit.com/product/1404

UPDATE: Looks like sparkfun had a server crash due to a snowstorm?! Facebook says they'll be up as soon as possible.



Edited 2 time(s). Last edit at 2019-03-13 05:05 PM by lokiufgator.

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ohlord Avatar
ohlord Gold Member Rob C
North of Seattle, N.W., USA   USA
1957 Land Rover Series I "EYEYIYI"
1971 MG MGB
1971 MG MGB "Bedouin 2"
Linear actuators.
12V programmable or arduino programmed
Even control idle speed increase on A/C demand



"I'm a long way gone down this wild road I'm on
It's gonna take me where I'm bound
It's a long way around"



"These are the days that must happen to you"

RD2 Radar/ Electronic Warfare Technician
Vietnam 1969-1972

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tvrgeek Avatar
tvrgeek Scott S
Hillsborough, North Carolinia, USA   USA
1965 MG MGB
Mike, I had not seen that board. I'll have to get me some. Sweet. I was already having issues with not enough memory on the Arduino and the speed was marginal for my dwell/tach meter. It might be fast enough to build an ignition controller. Too many projects! I can't get anything done since retiring. Boy do they have some nifty stuff.

I think some of the vacuum servos are just on/off so they would use two doors, one defrost, one heat. Don't know how they do proportional on the water valve though.

How will you determine where the servo is is without a power cycle or resolver? I have not worked with position servos before. This is why I was looking at using Vintage air valve minus the valve for the door and a switch wit resistors for position. A bit of epoxy casting and use the OEM knobs but I have not found a knob for the fan that looks right.



Cogito ergo sum periculoso

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B-racer Avatar
B-racer Jeff Schlemmer
Shakopee, MN, USA   USA
1950 Willys Jeep Pickup "Ratrod"
1971 MG MGB
2014 Dodge Charger
Just use a Megasquirt and tie in the A/C for an idle speed bump with the IAC.



jeff@advanceddistributors.com

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tvrgeek Avatar
tvrgeek Scott S
Hillsborough, North Carolinia, USA   USA
1965 MG MGB
If and when I do EFI, I would. That was a different question on how to do idle stabilization for AC and if one could bugger a cruise control, but the are too slow. I have not given up on doing idle stabilization on SUs but have too many other projects on my plate.

Here I was looking to understand how the vacuum servos in HVAC work proportionally On/off is easy to see, but how does one move part way? I want to replace the binding clumsy Morse cable controls with nice smooth operating controls. For $80 one gets the servo valve form Vintage. Easy and popular. I already have a 4 position fan switch, but was looking at the best way to control the flap door. 3 positions would work. I have not dealt with RC servos so I do not know how they know what position they are in without some sort of sensor.

Just thinking, a three position toggle would be even more intuitive. Up for defrost, strait for both, down for floor. I bet one could bugger a Headlight switch to do this. I was also thinking the low speed for my fan is not really useful and just going medium and high, so again, one could use a Lucas switch for the fan. This is keeping with the dash "character" of my 65.

A sideways question is with the water flow paths in the MG, is there any advantage to a 4-port heater valve to have water flow through the heater path but bypass the core or would this just be bypassing some of the engine you are trying to cool. Both valves are available. 4-port are common on modern cars, but MG used 2 port.



Cogito ergo sum periculoso

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lokiufgator Avatar
lokiufgator Gold Member Mike S
Evington, VA, USA   USA
Scott,
Using the Trinket's analog inputs I'm using the potentiometer as a voltage splitter and then have a little program that loops through reading that input. It then controls the servo through PWM to have it move to a specific position. That slider pot is really nice and smooth if I do a full custom console and then print stickers to show which is floor, mix, and defrost. If you wanted to do it with a 3 position switch you would just have to play a little with what resistors to put into each of the outputs, something real low 10 Ohm for say floor, 5k Ohm for mix, and then 10k or 20k Ohm for defrost to give the voltage splits needed for positioning the servo. I'll upload a video later tonight when i get home of it running with the slider and the little project box I put it in to make it a self-contained, easily removable brain all connected by RC servo connects.

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riley1489 Avatar
riley1489 Gold Member Bruce H
Great White North, QC, Canada   CAN
1953 Jaguar XK120
1959 Riley 1.5 "King George"
1973 MG MGB
.



Check your ego Amigo!



Edited 2 time(s). Last edit at 2019-03-14 11:53 AM by riley1489.

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tvrgeek Avatar
tvrgeek Scott S
Hillsborough, North Carolinia, USA   USA
1965 MG MGB
I get how to tell it to move, I just don't know how it knows where it is. I'l l start reading on the robotics forums I guess as a break from leaning on an idiot stick.



Cogito ergo sum periculoso

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Gerald O Avatar
Gerald O Gerald O'Docharty
Wake Forest, North Carolina, USA   USA
1972 MG MGB GT
1978 MG MGB
In reply to # 3908594 by tvrgeek I get how to tell it to move, I just don't know how it knows where it is. I'l l start reading on the robotics forums I guess as a break from leaning on an idiot stick.
Usually, seek to home first, via a home position sensor like a photo interrupter flag, or hall-effect. Then count number of positioning steps to seek to position. Think old floppy drive head positioner (leadscrew), or printer carriage stepper (belt).

Oh, if it's a rotary servo, then it will have a potentiometer connected to the geartrain for proportional position control. Voltage on the pot coincides with position.
If you want to cook your own control, then use a comparator with the position pot connected to one input, and a 'control' voltage connected to the other input. The comparator output toggles up or down to control an H-bridge that drives the motor direction (for brushed DC motor). There's a bit more to it, but that's the principle.



Edited 2 time(s). Last edit at 2019-03-14 12:11 PM by Gerald O.

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tvrgeek Avatar
tvrgeek Scott S
Hillsborough, North Carolinia, USA   USA
1965 MG MGB
Ah, it will have a resolver built in. That is what I did not know. For a flap door, we don't need the precision of self calibration based on the two extreme positions. We did all that for tape loops, but talking just a heater door. With a flexible lever, we can even overshoot a little.

Done moving dirt for the day, I can start googling stuff.



Cogito ergo sum periculoso

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tvrgeek Avatar
tvrgeek Scott S
Hillsborough, North Carolinia, USA   USA
1965 MG MGB
On an adafruit tutorial " Position pot on the armature" So, a resolver is built in. That is what I needed to know.
Guess I need to order some stuff and start playing.



Cogito ergo sum periculoso

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  ohlord thanked tvrgeek for this post
ohlord Avatar
ohlord Gold Member Rob C
North of Seattle, N.W., USA   USA
1957 Land Rover Series I "EYEYIYI"
1971 MG MGB
1971 MG MGB "Bedouin 2"
thumbs up



"I'm a long way gone down this wild road I'm on
It's gonna take me where I'm bound
It's a long way around"



"These are the days that must happen to you"

RD2 Radar/ Electronic Warfare Technician
Vietnam 1969-1972

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lokiufgator Avatar
lokiufgator Gold Member Mike S
Evington, VA, USA   USA
So I promised you guys videos. Here you go!
I can't put up video files so let's see if you can see them in my google drive account.
https://drive.google.com/file/d/10JLThGTJT3kd6x7CEUtSSIkBbIzZ0mwH/view?usp=drivesdk

https://drive.google.com/file/d/1Sl9xGk6I6FjOQa3zSMCb2O0f1WkC3vO9/view?usp=drivesdk

https://drive.google.com/file/d/1pzaxtiE7JUs50dUss5IO3ipdwofrfgPg/view?usp=drivesdk

Let me know if they work.



Edited 1 time(s). Last edit at 2019-03-14 09:10 PM by lokiufgator.

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tvrgeek Avatar
tvrgeek Scott S
Hillsborough, North Carolinia, USA   USA
1965 MG MGB
Yup.

You have it go home on power up rather than just stay where it is?



Cogito ergo sum periculoso

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