IntelliPlug desktop teardown (updated with findings of zero crossing claims). - Page 1
Forum section: electronics / general

author: Kibi
author_rank: Unknown
timestamp: January 23, 2012, 08:23:06 pm
content: A few years ago my father gave me one of these IntelliPlug power saving devices. It is designed to monitor the current going out of the master outlet and switch the peripheral sockets on or off. Usually, you'll connect your PC to the master outlet and then when you switch the PC on the IntelliPlug will sense the current and then switch on the other peripherals such as monitor and printer. The idea is that you'll save energy by not having the peripherals sitting in standby.I had never used it before because I was a bit sceptical about how it works, I thought it might be a bit crappy, perhaps employing a triac for switching the loads and be of mediocre quality.I did however think about using it on my bench to switch all my tools off when I switch the bench light off. My Agilent DSO for instance uses 6W (10VA) in standby. Dave did a rant video about this too. It also has the benefit of being a bit safer having your tools switched off. I have forgotten to switch my soldering iron off on more than one occasion.So before I used it, I thought I would take it apart.Nice good quality fuse.Weird screws, probably to prevent tear downs, but the first flat blade screwdriver I picked up fitted just right. So much for that.I was quite pleasantly surprised when the lid came off. Nice quality FR4 board and good protection devices.The power supply is designed around a Power Integrations LNK302. It's a low component count, energy efficient switcher chip. Not some crappy capacitor and resistor voltage dropper design with no feedback.Now, it does actually employ a proper energy monitoring device. They have gone for a Cirrus Logic CS5466.The IntelliPlug brochure stated that it can even detect the zero crossing points to switch the loads on and off at those points to reduce stress on the loads. Although that sounds impressive and the Cirrus Logic can easily detect the zero crossing points, I'm not too sure how accurately the device performs in that regard since they are employing a relay (slow transition time) to switch the loads.Overall though, I was very pleasantly surprised. The quality and the design of the product greatly exceeded my expectations.

author: phil_jp1
author_rank: Regular Contributor
timestamp: January 25, 2012, 01:02:12 pm
content: Pretty nice internal construction indeed!I'm guessing that it is perfectly possible to make it turn on at zero-crossing, because relay pickup time should be pretty consistent each time with stable supply voltage.When I was testing relay release time here:http://jumperone.com/2011/10/using-relays/I also tested relay pickup time, and I did it a couple of times with different relays (same relay type, same manufacturer), and it was consistent. Don't remember how many milliseconds it was, though.

author: Kibi
author_rank: Unknown
timestamp: January 25, 2012, 07:14:04 pm
content: That's very interesting. I might like to actually take it apart again and make some measurements with respect to the transition times and how close to the zero crossing points it actually switches. I'll see how this weekend goes.

author: nukie
author_rank: Frequent Contributor
timestamp: January 26, 2012, 01:11:13 pm
content: Very nice thanks for sharing. Always wondered if they contain any snake oil. Seems like they dont. Glad to know that it actually works!

author: RJSC
author_rank: Regular Contributor
timestamp: January 26, 2012, 06:28:55 pm
content: Doesn't this seem like over-engineering to you?So much components, probably expensive, for such a simple task.A current transformer and a comparator would do it just fine, probably much cheaper, I guess.

author: phil_jp1
author_rank: Regular Contributor
timestamp: January 26, 2012, 11:59:05 pm
content: Quote from: RJSC on January 26, 2012, 06:28:55 pmWhy do you think that? Which part looks like over-engineering to you?

author: Kibi
author_rank: Unknown
timestamp: January 27, 2012, 09:15:37 am
content: Quote from: RJSC on January 26, 2012, 06:28:55 pmWell, a simple CT would work, but then at what threshold to you design the device to switch on or off. You could put a pot. on the side to adjust the threshold but you then have to program the user to adjust it accordingly. Having a threshold of 5W for instance would not necessarily work because the standby power of the device plugged in to the master outlet may be more than 5W meaning the device would not switch off. Then again it may be less. Your average Joe doesn't want to be fiddling about, he just wants the device to work as advertised.Having some degree of "intelligence" built in to the device makes it more practical to use.

author: Kibi
author_rank: Unknown
timestamp: January 29, 2012, 02:51:57 pm
content: Quote from: phil_jp1 on January 25, 2012, 01:02:12 pmI had a moment today to confirm whether the zero crossing claims are founded or not.I pulled the plug apart again and de-solderd the wires from the LED on the front. The LED comes on when the relay is energised and the loads are switched on. I used an electric lamp plugged into the "master" outlet and a crappy AC step down transformer to one of the "peripheral" outlets.I connected the transformer secondary up to CH1 (yellow trace) of my oscilloscope.The device's LED leads connect to CH2 (green trace) on the 'scope via an opto coupler just to be safe. I had no idea if those LED leads were floating at mains potential or not.I then set the 'scope up on CH2 to trigger on the edge of the signal for the LED. This signal also switches the device's relay at the same time.The results were pleasantly surprising.Here is the 'scope triggering on the rising edge as the relay energises and switches the peripheral loads on. It's not exactly on the zero crossing point of the mains, but reasonably close.Here is the result of triggering on the falling edge as the relay's coil is de-energised and the loads are switched off. Again, not exactly on the zero crossing point, but close enough. Notice how the relay contacts open quicker on de-energising than they do when closing upon energising. It would seem that they open a little bit too soon. You can even see the back EMF spike coming off the transformer. It would not do this if it were switched off at exactly 0 volts.I repeated this experiment several times and it consistently produced the same results.My thinking is that the zero crossing signals coming out of the CS5466 are passed to the micro controller which is programmed to de-energise the relay slightly ahead to time to give the relay time to react, the designers probably decide how long this time should be based on measurements taken from the relay they intend to use.I'm not too sure how much better off your loads are by having them switched on at the zero crossing points, I don't wait for zero crossing points when I switch my kettle on in the morning, but I'll bet it saves a lot of arcing of the relay contacts over time.Now all I have to do is fix the date on my oscilloscope.

author: jahonen
author_rank: Super Contributor
timestamp: January 29, 2012, 04:35:19 pm
content: Nice measurements.I think that the correct point to switch off the voltage to a purely inductive load is at the peak voltage, where the current is zero (90 degree phase shift!). In that respect, zero cross switching is not optimal for inductive loads.Regards,Janne

author: white_sw
author_rank: Newbie
timestamp: January 15, 2013, 02:48:37 pm
content: I have been reading these forum's for sometime now but never registered. I've always been interested in electronics as a hobby but never had any sort of training. I mainly use electronics for my model railway and radio control projects. I too have taken apart an Intelliplug out of curiosity. I'm hoping somebody maybe able to offer me some guidance/advice as I would like to, potentially, modify my intelliplug so the start up of the peripheral device is quicker. Within a second of the primary device starting instead of 5-6 seconds. But I don't really know where to start. Could somebody point me in the right direction for my research ?Thanks,Sam

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 15, 2013, 03:38:26 pm
content: I'd agree it looks a little over-engineered.Was surprised to see that LNK302 PSU in there - for low power stuff like this, a 48V relay (48V to reduce coil current) and capacitive dropper would typically be a cheaper approach. And using a dedicated sensing chip for what is basically simple currrent sensing seems like overkill.OK this unit might perform slightly better in a wider variety of cases, but is the additional cost justified?

author: dr_dan
author_rank: Contributor
timestamp: January 30, 2013, 10:21:16 pm
content: First of all, thanks for a great tear-down - on the basis of this thread I bought a couple of these units (£4 each including delivery directly from e-on's on-line store!) to use as dust-extractor switches for use with power tools. I've modified them to reduce both the turn-on and turn-off delays, and added a push button to provide an override. I also control the LED independently of the relay, to give a basic status display. If anyone is interested, I'll post more about that.I suspect the reason it looks over-engineered (especially the power supply) is that the same PCB is used in the "Laptop" Intelliplug which is essentially the same unit but with an RJ12 socket on the right hand side.I don't have the laptop version but from what I've seen on the web it has a RJ12-USB cable that you need to plug into your computer to allow / help the intelliplug to switch at the correct time.The pads for the socket are present on the underside of the board, the pins appear to be routed directly to the smaller IC, so I can see why they'd choose to use a 'proper' 5v supply.

author: white_sw
author_rank: Newbie
timestamp: February 02, 2013, 10:51:31 am
content: I would really like to know more about your modifications to the IntelliPlug for using to control a dust extractor as this is exactly what I am using them for. I've been trying to work out how to reduce the auto on/off times. A push button override would be a nice too.

author: darkhorse0
author_rank: Newbie
timestamp: March 16, 2013, 10:50:56 am
content: Hi Dr Dan, i'm very interested in how you altered the delay on the relay, any chance of a breakdown of how you did it?Thanks!

author: dr_dan
author_rank: Contributor
timestamp: March 31, 2013, 09:04:06 pm
content: Hi Darkhorse,To modify the time delay I grafted a small microcontroller (8-pin DIL PIC12C508A) into the Intelliplug. I tapped off the "FOUT" pulse output from the CS5466 (U2) and fed that to the PIC. I cut the track that linked the control IC (U1) to the relay and LED drive transistor (I used a drill bit on the via next to R1 to break the connection) and drive the base of the transistor from the PIC through the base current limit resistor R8.5 volts is readily available from the pads at the bottom of the board.I used a PIC12C508A simply because I had some to hand. Since the PIC has 6 GPIOs and I only really needed 2 of them I added a few extra features - I added a momentary push button and chose to control the LED separately from the relay.The LED gives a slow flash when the unit is idle, is on steady when power is being drawn through the sense socket above a set threshold, and flashes rapidly while the relay is only being held on by the turn-off timer.Pushing the button toggles between idle mode and override (for when you just need the extractor running). The LED flashes at a medium rate during override mode. If you operate the power tool during override mode, it switches back to normal mode automatically.Turn on time is about half a second, turn off is about 1.5 seconds. These seem about right for use with a hand-held circular saw.It's worth noting that with the modification as it stands I haven't tried to retain the zero-crossing switching feature nor the 'learning' of the original intelliplug.I'm planning to write this up properly when I've got time and will post the PIC source code.Regards,Dan

author: FailSnail
author_rank: Newbie
timestamp: December 13, 2015, 02:42:58 am
content: Hi guys, long time reader but first time poster.Sorry about resurrecting an old post but I was wondering if I could ask a question that you guys might be able to help me answer.Here goes!I have brought several of these Intelliplug devices to control household appliances, the ones I purchased have Infrared and can learn a command signal from a remote to turn on and off. I am looking for a way to disable the smart functionality of the device to stop it turning off the plug when there is a voltage drop. I want to use them only via the IR for a simple on/off.I am hoping it will be as simple as drilling through a track to stop a signal getting through. Do you guys have any idea how I would go about this?Thanks in advance for your help

author: FailSnail
author_rank: Newbie
timestamp: December 13, 2015, 08:25:48 pm
content: Anybody got any ideas? Any tips would be amazing