Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Hi Kiss,
Sorry for the delay each time, every time I get back to the site I have to log in & for some reason I can't get to the log in page, it takes many tries to get it?
When I turn the pot into the Arduino Down I can get the voltage from the triac down to around 25V Ac but then near total zero of the pot the triac output jumps to 40V Ac output, hence the sine wave in the video at zero input from the pot.
If I change the cap as mentioned it changes the amplitude of the triac output when the pot is totally off.
I don't think it's hum due to the fact of the amplitude of the output when changing the cap value.
I have the Triac connected directly to the primary winding, the secondary winding has the 100uF cap & the 6Ω resistor as the load.
The probe is connected to the Active leg on the primary side of the transformer, ground clip to Neutral .
Somebody Turned up so I cut my explanation a bit short before, sorry.
The circuit works very well to 240V output, it's only the issue at near turn off of the pot into the Arduino where the Voltage from the Triac continues instead of being OFF.
By changing the cap values the triac output varies. The Triac is being triggered on by something instead of turning off, there is no gate signal when this is happening.
At the moment if I turn on the mains power to the circuit the Triac output is 40V without a gate signal being applied ( Arduino Off--Disconnected) but the Triac is still being Triggered?
Before with a different cap value the output of the Triac was much higher & you could here the transformer working with no gate signal or power to the Arduino, just the mains turned on to the Triac Circuit.
Hi Kiss,
I found the problem:
I had a BTA16 Triac in the circuit which has dubious ST markings on it like I mentioned before so I tried another & another with the same markings with no luck.
I then went down to my Flow Test bench & removed an original ST BTA16 from the circuit & tried it in this & presto I can adjust down to 33mV & no sign of the sine wave at pot switch off.
This had me buggered for quite a while, I know I don't know much but I could find no reason for the issue?
It is now working beautifully!
Hi Kiss,
Yes, very excited now actually.
Yes now the biggy, PID.
I have just been trying to work out something suitable to control on the bench, I have an idea but have to go & have a look at what I have to set it up properly.
Almost Tackled this project?
I wish, I still have the BCD Switch problem I was having to overcome & many more things that pop into mind.
One thing at a time though, I will try to control something first with the Transformer on the bench to see how I go.
One thing is open loop control of a universal motor.
All of the PID stuff that I did that operated into a transformer required current limiting, but the currents were pretty high.
All used back to back SCR's. The SCR units were 2.5x oversized and the fuses were one EXPENSIVE one on the SCR unit and one cheap one.
Shorts were somewhat common events, but blowing a $1.00 fuse was preferable to blowing a $35.00 fuse.
Fuses to protect SCR's/Triacs are know as semiconductor fuses or I2t fuses.
So, I don't know if you will need current limiting or I2C fuses
We did a lot of it, until I put my neck on the line and said, this is ridiculous.
Instead of a custom panel that:
Didn't read power correctly with analog meters, but they were able to monitor the process.
A custom panel with a Variac, Voltage and current meters and sometime a temperature readout that tool up a HUGE amount of space I suggested a 1 RU (Rack Unit) DC power supply and a ramp/soak controller. SO about $2500 USD per source. Typically we required up to seven power supply systems per research unit.
We had to upgrade to something because the outputs of the controllers were becoming standard (i.e. 4-20 mA) and not proprietary.
It would have been nice to have a "power readout", but we didn't have that anyway.
In one case they wanted true power and I found a 3 phase power meter that would operate at low voltages and they used that for 1 source.
Hi Kiss,
Just one question before I forget, with back to back SCR's as you have mentioned, do you fire one SCR for the Positive half wave & then the other for the Negative half wave.
Is that how it works, just interested to know!
Yes, I see what your saying with current limiting & also working with not enough good equipment to do the job properly, it makes things hard & a real headache.
Yes, of course the project is about controlling the Universal motors, I just thought that if I can control something small on the bench first & get all my set point circuits made properly & everything operating as it should I can then setup the Universal Motor control easily.
This would allow me to have a relatively relaxing time with minimal noise & excitement so to speak, as you know the universal motors are full of noise & vibration.
At the moment I am still inside at my work table & something small & quiet would be good to learn from.
I don't like your idea at all. Braking s NOT a way to control speed.I did a tension controller once, but I did not implement reverse voltage which makes the clutch less effective. It turned out we did not need it.
The one I came up with is to use a hair dryer.
1. They are inexpensive
2. Don't use heating
1. You could use pressure
or
2. use a resistor where you apply some voltage too, to make it slightly warm. Attach a fast response thermister to it and try to control it's temperature by cooling. It does make it a reverse-acting controller. Higher T, less fan.
2. The light bulb might work too, but instead of controlling the bulb, control the amount of forced air cooling from a hair dryer operating in "cool mode".
I still have the resistor across the traic output, it was 2.3K but I adjusted it to 3K now things are working correctly, this gets warm so I could control it's temperature with air cooling.
It has good insulation around the outside so should not be a problem.
Just one question before I forget, with back to back SCR's as you have mentioned, do you fire one SCR for the Positive half wave & then the other for the Negative half wave.
Is that how it works, just interested to know!
I still have the resistor across the traic output, it was 2.3K but I adjusted it to 3K now things are working correctly, this gets warm so I could control it's temperature with air cooling.
It has good insulation around the outside so should not be a problem.
Hi Kiss,
Sorry I have been reading previous posts about the Voltage Reference to the Aref pin on the Arduino.
I had a severe mental blank about this, which is not unusual but what I wanted to know is:
Can I use a 2.5V reference if my maximum voltage input to the Arduino is going to be 5V, basically, can a reference voltage be lower than the maximum input if it is a good stable reference voltage.
I found some LM336-2.5 Reference Diodes.
It seems from the datasheet that if LM336 is used with a LM317 the reference voltage can be adjusted higher than the 2.5V if that is not suitable.
Could you have a look at the datasheet for me & suggest which circuit would be best, I was thinking that (Figure 2, page 5) or the circuit using the (LM317, page 6) would be good?
Hi Kiss,
Sorry, forgot to comment on the Blower-AKA hair dryer, I actually thought that it was a good idea & you can get them cheaply as my wife has said.
My wife has offered up her Vacuum Cleaner under the conditions that if I blow it up she gets a new one haha!
I have decided to use the vacuum cleaner as it is of course a universal motor, I can connect a manometer onto it & use the MPX2010DP sensor as will be used in the final setup.
The noise is not to bad with the motor being enclosed so it should be good to go.
It has a variable speed pot so I will just bypass that, it should be good to test the PID out.
I would still like to know about if the reference voltage can be lower than the maximum input voltage, I have done a fair bit of reading & some say the reference voltage basically can be say 2.5V & the input can be higher & others say the reference voltage should be the same as the highest input voltage so I am still unsure about this.
I have read that the Arduino Mega 2560 like I have has internal reference voltages of 1.1V or 2.56V so if the 2.56V can be set & used this would be good?
The reference should closely match the anticipated max sensor output. The only reason is to get the most resolution. If you expect 0.7 out, then a 5V reference doesn't make sense. i.e. 1/256 of 1.2 (reference) is better than 1/256 of a 2.5 V reference for a 0.7 V max sensor.
The reference voltage can only be up to the processor power supply. Some of the new Arduinos are 3.3 V.
The pressure sensor isn't your typical automotive sensor. It basically requires an instrumentation amp. If you really wanted to calibrate it,you need to compensate for a small offset. There are some single supply zero offset IA's that we'd have to select. Generally the importance is to drive the output reference of the IA with a low Z source.
In an automotive environment they use sensors that are called "ratiometric" They are powered from 5V and the reference to the A/D might be 1/2 Vcc. That means whatever Vcc is. It could be 5.1, 5.3, 4.9 or whatever. So, the reference tracks the instantaneous output of the power supply.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
