Components for Converting AC->DC + voltage step-down + reversing of polarity

Can you run a similar test while measuring the voltage across the motor? You can check that the voltage is reading correctly as it should read close to 9 V when connected directly to the power supply.

Nigel Goodwin said:

I think you're rather optimistic how fast fuses blow, and I presume resettable ones are no different? - generally you need a massive overload to blow it quickly, something like 10A through a 5A fuse could well take minutes before it blows, if it even blows at all.

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Hi Nigel -- yeah, agree, think I am rather optimistic here... what has confused me is the manufacturer's tool (which the circuit is listed above), includes a Resettable Fuse that seems to trip very quickly and essentially stops the motor right away in both directions and doesn't seem to get too hot.

I just discovered an obvious/simple issue that was causing me to scratch my head a bit last week.... I blew a fuse in my multimeter.... ugh. That slowed me down a bit and I'm still waiting for a low current replacement fuse.

However, since that time, I did receive some more components and put the following resettable fuse in serial to my DC Actuator:


This is a 100mA hold and 200mA Trip and it actually seems to trip fairly quickly.

I also finally got my Relay Sockets and have stuff wired up a lot cleaner.

Please see the following video:


BTW, apologies for the long "wait time" in the middle of the video, you can fast forward from: ~60 seconds to: ~1min 50 seconds to avoid the wait time before the Actuator Close begins... (BTW, sometimes better to Download the video vs. trying to stream as Google Photos tends to limit stream bandwidth)

Diver300 said:

Can you run a similar test while measuring the voltage across the motor? You can check that the voltage is reading correctly as it should read close to 9 V when connected directly to the power supply.

Click to expand...

Diver300, as you can see in the video, the voltage doesn't really come down much at all....even when the motor is stopped. I don't assume the 6v max Fuse in the Hand Tool would have any effect on things, right?

****EDIT**** Pretty sure the way I tested Voltage in the video was not the right way (at the relay outputs), so I re-tested for Voltage directly across the motor during a Close request. Shortly after the mechanical limit on the actuator shaft hits the housing, it goes from 9v -> 6v in like 1-2 seconds, and from there, it drops almost immediately and stabilizes around .6v-1v while the Resettable Fuse is heating up....****EDIT****

However, I ran into another unexpected issue. Most of my previous testing was with the Open Damper command.... and for whatever reason, even though the Damper Actuator Travel Time is a configurable option, that is specific only to the "Closed to Open" Travel Time, not the reverse...

The Open to Closed Travel Time does a "static" 2min 30second CLOSE as you saw in the video...

So, during the Close function, the Resettable Fuse is heating up for a good 2min30 seconds... and the one I have installed above gets up to 216 degrees F.... so quite a lot hotter than the factory tool (~136 degrees)... Hmmmm

So, I'm wondering how unacceptable that is. I'm trying to get the manufacturer to allow the Open to Close Actuator Travel time be configurable so I can make Close 20 seconds too, but not overly confident they would be willing to make that change.

I have a handful more Fast Blow Resettable Fuses arriving on Tuesday to see if I can find one that reacts quicker (you can hear the motor get buried for a coupe seconds before it stops) and doesn't get as hot...

The question I have now:

Does it seem like I'm going down a decent path still... or is there another idea/option to better manage load/heat for this application? Again, I'm willing to spend some money to ensure it's as reliable and industrial strength as I need it to work for 30+ years...

Thank you guys!

whytwo said:

Diver300, as you can see in the video, the voltage doesn't really come down much at all....even when the motor is stopped.

Click to expand...

You have the multimeter connected across the series combination of the motor and the fuse. That will always stay near 9V because the power supply is doing its job and the relays are not dropping the voltage.

What I was looking for you to do was to connect the multimeter across the motor only, where there will be a large change in voltage.

I think that all resettable fuses will get hot when tripped. That is how they work.

whytwo said:

****EDIT**** Pretty sure the way I tested Voltage in the video was not the right way (at the relay outputs), so I re-tested for Voltage directly across the motor during a Close request. Shortly after the mechanical limit on the actuator shaft hits the housing, it goes from 9v -> 6v in like 1-2 seconds, and from there, it drops almost immediately and stabilizes around .6v-1v while the Resettable Fuse is heating up....****EDIT****

Click to expand...

That is the sort of behavior I would expect.

If you just reduce the voltage of the supply, the motors will run more slowly and there will be less force when they first hit the end stops. You may be able to adjust the voltage of the supply, even if it's to find the right voltage before getting a lower-voltage one.

Also, the self-resetting fuses will get hot. Reducing the voltage will only reduce the final temperature marginally.

Can you mount the self-resetting fuses remotely, so that they are easy to replace if needed?

Diver300 said:

If you just reduce the voltage of the supply, the motors will run more slowly and there will be less force when they first hit the end stops. You may be able to adjust the voltage of the supply, even if it's to find the right voltage before getting a lower-voltage one.

Can you mount the self-resetting fuses remotely, so that they are easy to replace if needed?

Click to expand...

I really like this line of thinking... maybe I can tune everything so the motors have very little torque and stop easily without stressing the plastic actuator stop... I would want everything to be as gentle as possible!

I ordered some more Fast Blow resettable PPC that seem like good specs for this project and are supposed to blow in 100mS.... (Bourne CMF-RL50A-10) we'll see. I wonder if we bring the Voltage down, if it would take longer to blow the fuse?...

Either way, if the motor has less torque/power, if it takes 200ms vs 100ms, don't think it would matter much.

Would you suggest bringing voltage down by adding Resistors, or looking for an adjustable power supply??

Would be really nice to find a DIN mountable DC power supply adjustable from something like 5-10vdc, but haven't been able to dig one up this morning yet...

And YES, I can put the Resettable Fuses in a visible/available spot... some of the Resettable PPC specs I came across talked about 5000-6000 cycles as the limit, etc...

So maybe I can just replace them annually, etc.. (which would be plenty)

And as always, thanks again for all your feedback!

whytwo said:

Would you suggest bringing voltage down by adding Resistors, or looking for an adjustable power supply??

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I was suggesting an adjustable power supply or a fixed on at a lower voltage.

A resistor wouldn't do a good job as it wouldn't reduce the speed as much for the same stall torque.

You could put diodes in series with the power supply. You will loose about 0.7 V per diode, so four or five in series will take your 9 V supply down to about 6 V.

Looks like XP Power (the company that makes the 9vdc DIN mount supply I currently have) makes a 5vdc 15W 3Amp, and a 5vdc 30W 6Amp...

They don't appear to make a 6v.

Would either of those 5vdc supplies make sense or is that too little voltage?? More Wattage or less??


Thanks again!

Just another quick update -- I ordered a couple different DIN mountable Pheonix Contact Power supplies:



I'm hoping the up-to 6.2vdc power supply works -- I'll try that first before opening the other unit so I can still return the more expensive one if not necessary.

Will update again soon when I get more stuff.

whytwo said:

Would either of those 5vdc supplies make sense or is that too little voltage?? More Wattage or less??

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I don't know how much voltage you would need. The maximum motor torque and the maximum speed will reduce with voltage and that would need testing.

As long as you have enough current to run however many motors you want to run at one time, there is no point in getting a larger power rating.

If the motor is working hard (less RPM) then there will be less BEMF and the motors will take more current. The voltage just gives the maximum RPM (no RPM = no BEMF = lots of loverly current) - the AMPs give the torque. As Diver said, "If you have enough current" then everything else will fall in place.

Mike.

Just wanting to come back for an update -- I'm still working on optimizing this solution.

I am receiving another round of PTC fusses to do more testing early this week.

I did receive a 6.2vdc DIN rail power supply to test the motors at a lower voltage, and like everybody said, they do work and simply turn slower, etc.. Current draw is almost the same at 6v vs. 9v.

I had been wondering about whether lower voltage and maybe slightly less current would cause a Resettable PTC to take longer to blow....so I went back to my 9v power supply (haven't confirmed that yet, however, I did run into an issue.)

Somehow, I made simple mistake and left the circuit connected WITHOUT a Resettable fuse and walked away...

Came back later and the stop on my new motor was broken... ugh. (the HVAC controller closed the Damper when I was away)

So that has set me back a little -- I should get 2 more DC Actuator Damper motors for more testing today...

I have continued thinking about a more resilient/reliable solution. (again, I simply cannot have the motors behind drywall break.... is not an option to leave the Dampers open/closed/partial and then stuck...)

I agree with Diver that it would likely complicate things and probably not work as well..


Any chance the "more complicated" way of a Current Limiting Circuit with an output to something like a Raspberry Pi, which could read the current and trigger a Relay that would STOP the current immediately for 3 minutes when current goes higher than 100mA? (it could also seemingly account for Inrush current in the coding)

Realize there would be some programming/scripting at the very least here, but is this possibly a more enterprise solution?

Thanks everybody.

The programming for a Raspberry Pi is probably quite simple, although I've no personal experience.

What I do know is that you will need to measure the current and feed the signal to the Raspberry Pi. You will need either:-
A shunt resistor and a suitable amplifier
or
A Hall-effect current transducer.

You will also need 5 V relays (or transistors and higher voltage relays) to let the Raspberry Pi control the motor.

Thanks Diver, I came across this Hall-Effect device already a number of times... and using a transistor to a higher power relay makes sense since I would be working off of signal, not Line Voltage.

If I got something like the above designed, would it make sense that when the micro controller reads current over X, it sends signal to transistor to switch a relay that would break the relaying that is Contacting my Damper Actuators??

i.e. this current detection circuit that has a relay is in-serial with the existing relay and its NC position would be to let the current flow unless triggered by this setup? (which would break the Damper current as soon as the motor stalled in either direction?)

Diver300, any chance something like this could work?


Looks like it's an adjustable Current Sensing relay with either Transistor OR SPDT contact output...


Maybe I could trigger a timer relay to break contact of the 24ac Open/Close supply current for 3 minutes (to make sure it goes around the long Close command)

Hmmm... thoughts?

whytwo said:

Came back later and the stop on my new motor was broken... ugh. (the HVAC controller closed the Damper when I was away)

Click to expand...

Maybe the 6V supply will allow the motor to stall without breaking the stop. Or, you could add limit switches.

Mike.

whytwo said:

Diver300, any chance something like this could work?

https://www.ia.omron.com/products/family/3491/lineup.html

Looks like it's an adjustable Current Sensing relay with either Transistor OR SPDT contact output...

https://www.ia.omron.com/products/family/3491/specification.html

Maybe I could trigger a timer relay to break contact of the 24ac Open/Close supply current for 3 minutes (to make sure it goes around the long Close command)

Hmmm... thoughts?

Click to expand...

The problem with those is that you need to allow for inrush current as the motor starts, and you don't want to allow that long when the motor stops. However, give it a try.

As you are interested in current profiles over time, you really need an oscilloscope to measure that (with a shunt resistor as oscilloscopes can only measure voltage)

My suggestion is:- https://www.picotech.com/oscilloscope/2000/picoscope-2000-overview

Diver, thanks again for your recommendations.

I've been thinking about getting an oscilloscope, so I think timing is good to pick on up!

After researching this today, I thought the following could be good:


This is a 4-channel, 1Gs sample rate @ 70Mhz -- does this seem sufficient for this and future projects?

Additionally, I ordered the following relays:


The relay about has a variable start delay to handle Inrush current variants, responds in 100mS and should be able to be tuned to around 65mA...

I also ordered:


My thinking is I can connect the current monitoring relay to trip the Time Relay which should be able to be configured to trip for 3 minutes.

I'm hoping the outputs of this Time Relay can "disconnect" power to the Damper Actuator.

Does this seem like it could work?!

Thanks again,

The relays should work. There are various settings which will be needed, and the circuit will be fairly complicated but that can all be tested.

The oscilloscope is overkill for a project like this. You only need one channel to monitor the current. All oscilloscopes come with two, so that leaves a spare in case you need to check some other timing relative to the current.

70 MHz bandwidth is far more than you need, and adds a lot of cost. Lower bandwidth is fine. You are only needing to know how the current is changing on timescales a bit faster than the eye can see and multimeters can follow, so you realistically only need 10 kHz bandwidth. Oscilloscopes generally only start at 5 - 10 MHz bandwidth, so any oscilloscope is fast enough.

Also, you only need 8 bit resolution. That could measure 10 V with steps of about 0.04 V.

I can't see bandwidth over 10 MHz ever being needed in HVAC applications. I would get the cheapest Pico tech one. If you use that, and find that it has limitations, it will have cost very little compared to the difference between expensive ones.

Diver300 said:

The relays should work. There are various settings which will be needed, and the circuit will be fairly complicated but that can all be tested.

The oscilloscope is overkill for a project like this. You only need one channel to monitor the current. All oscilloscopes come with two, so that leaves a spare in case you need to check some other timing relative to the current.

70 MHz bandwidth is far more than you need, and adds a lot of cost. Lower bandwidth is fine. You are only needing to know how the current is changing on timescales a bit faster than the eye can see and multimeters can follow, so you realistically only need 10 kHz bandwidth. Oscilloscopes generally only start at 5 - 10 MHz bandwidth, so any oscilloscope is fast enough.

Also, you only need 8 bit resolution. That could measure 10 V with steps of about 0.04 V.

I can't see bandwidth over 10 MHz ever being needed in HVAC applications. I would get the cheapest Pico tech one. If you use that, and find that it has limitations, it will have cost very little compared to the difference between expensive ones.

Click to expand...

We went to a Water Industry trade show a few years back (we've not been recently, due to Covid and various problems - like heart attacks ) and one of the stalls was showing oscilloscopes specifically designed for use in electrics, rather than electronics.

I had a little play with it - as you do - and it was essentially a fairly standard LCD digital scope, but ruggedized, and with higher input voltage ranges than most normal scopes have.

So there are scopes out there specifically designed for the sort of application the OP is looking for.

Diver, thanks for the recommendation on the specs -- I stepped down my specs down a bit and just ordered a PicoScope! Like I said, I had been thinking about getting one for some time, so this was the nudge I needed.

I ended up keeping 4 channels since I have a number of other projects in mind that could definitely benefit from 2+ inputs. I have all sorts of other Home Automation projects going on where this may have been useful.

For reference, I'm not in the HVAC business...... (although at this point, I know more about it than I would have thought- ha).

This is my primary residence and a personal project of mine. I'm working towards implementing a commercial grade "Zoning" system... My house is 5 stories and was delivered with just a single Zone (technically), so I have issues in the Peak Summer and Peak Winter (Heat rises....). I'm trying to adapt a proper Zoning System to my current setup and believe I'm quite close (thanks to everyone's help here).

I'll follow up again when some of these parts start coming in...