Implementing a system based in Android + IOIO + relay problem + connector

[annlee]

Hi there, I am doing a system based on Android + IOIO board + Relay for a 230V/16A connector (I am European)

IOIO board only gives 3.3V output (not 5V), so I need a 3.3V relay that works for a 230V/16A connector, is there any relay with this specs?

or

should I need a MOSFET transistor between the IOIO board and the relay? which one?

Thanks in advance

 

[KFH]

Have a look a rs-components.co.uk for a relay.

 

[annlee]

Have a look a rs-components.co.uk for a relay.

Seems there is nothing there...

 

[Rockingit]

If you can't find a 3.3v relay, then yes, you'll probably have to build a driver circuit instead and use that to switch a 5v relay which are readily available. You might want to look at the load you're switching and possibly elect to use that low voltage relay to switch a 230V contactor?

 

[grantr37]

Hello Annlee, sorry for the delay, I was on here an hour ago and my account logged itself out again, before I got to sign back on there were 2 phonecalls to me and a text message which delayed me in getting back to my laptop, I have a solution for you and I will put it onto here now in 3 sections as it is quite long, please print this out to read and keep and I will do a circuit diagram if you need one, but that will need to be tomorrow as I have to log off soon and go away for a while.
please feel free to ask me any questions you may have....

 

[grantr37]

Section 1 for ANLEE:

Drive a 12v0 relay using a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) as a switch, use an OPTO Isolator such as a 4N25 (6 Pin DIL) as an interface for the switch Logic from the Output stage of the interface board at the control computer.
Provide the Vdd (Plus Volts) for the MOSFET Transistor via a 6v0 Voltage Regulator IC and a current limiting resistor to the Transistor Base, connect the Relay coil Negative Terminal (GND/Neutral/0Volts) to Collector and then the Emitter to Ground (VEE / 0 volts ) to act as an Electronic switch with the Transformer (power supply) connected the +Volts side of the Relay switch coil via a bridge rectifier, and an in line current limiting Resistor.
Use the 6v0 voltage Regulator output as the Drive source for the secondary stage of the OPTO ISOLATOR IC (Pin 4 - Pin 6) which will then drive the BASE of the Transistor and cause it to switch/energise the Relay coil, powering on and off the load each time the opto Isolator gets a 3v3 (3.3 volts) signal across pin 1 to pin 2.
Remember to use a small signal diode connected in series with pin 1 of the OPTO ISOLATOR and have this screened with a miniature ferrite bead shroud on the same small PCB (printed Circuit Board) as the Opto Isolator, you can give a better drive source for the 4N25 OPTO ISOLATOR by adding a cheap two input AND logic IC such as a 14pin (type 7408 TTL) AND chip with the output from the computer output board connected to pins 1 and 2 of the 7408 Integrated Circuit, connect pin 3 (the AND Logic output) to the input of the 4N25 IC OPTO ISOLATOR (this will provide 5v0 drive voltage with a marginally better current source characteristic) and can also use the same power supply as the Transistor and the OPTO ISOLATOR (all 3 components can accept the 6 volt supply from the regulator)

When constructing your power supply, it should be in this way :

( i )230v 500mA (0.5A) Fuse (inside an inline PCB solder tag fuse Holder)
(ii) primary Stage of Transformer (mains supply side)
Then :
(iii) The 12 Volt tap of the secondary windings of the transformer should be connected Via the Bridge Rectifier to the input pin of the 3 pin 6v0 voltage regulator IC which provides power to the 2 IC’s (the 7408 AND….the 4N25 OPTO ISOLATOR) and Q1(the Transistor)
The 12 Volts coming from the Bridge Rectifier (immediately after rectification) should also be connected to the supply terminal of the Relay Coil (remember that the Transistor connected between the Relay GND (Negative) and VEE Ground ( main Negative) Rail will do the ON/OFF switching of the Relay.

A single 1N400 Rectifier Diode should be connected in series between the Bridge Rectifier and the + Terminal of the Relay magnet coil to stop currents (spikes) developed by the collapsing magnetic fields of the relay coil de-energising from going into the Regulator IC and causing problems during switching (Flemmings right hand rule)

 

[grantr37]

Part 2 for ANLEE:

You will need, amongst a few other small low cost components:

1 X 230v/12v Step down Transformer

1 X 4N25 DIL (OPTO ISOLATOR)

1 X 7408 Quad 2 input NAND IC (14 pin) and also a PCB holder for this.

1 X 6v0 Voltage Regulator IC

1 X Bridge Rectifier

1 X 1N400 Rectifier Diode

1 X IN Line Fuse Holder

************Also some 230 V 500mA fast blow fuses***************

1 X Miniature Ferrite bead screen (hollow Iron tube to remove transients)
on input to the 4N25 OTPO ISOLATOR.

1 X NPN (NEGATIVE-POSITIVE-NEGATIVE) POWER Transistor
Such as a TIP3055 High power Transistor.

Access to a good selection of E12 Series Resistors (either ¼ Watt or ½ Watt

(1 X) 5v 5mm LED + 5mm LED Holder, you might want to add this to the
Input of the OPTO ISOLATOR to show when switching by the computer interface occurs.

Some Hot melt Glue (BOSTIK Glue) to make the security of the Transformer and Relay stronger after soldering onto your Printed Circuit Board.

(1 X) Heat Sink for the Voltage Regulator IC to take away excess heat from the case of the Regulator.

Consider using a 14 pin DIL Type 7400 NAND IC (Not And) to act as a Logic Latch with another separate input from the interface board, you can configure this so that the switching of the OPTOISOLATOR and therefore your Load/Relay may be either Momentary (only when the output from the computer is High/ 3v3) or it could be toggled (when the signal from the computer interface is 3v3) it goes High/ON and remains on until the next signal causes it to go LOW/OFF.
This Logic Latch circuit (set as a Flip Flop) could be turned on and off at will by the computer making the Latch feature selectable and enabling the user (or the software/firmware) to set the switching on the circuit (device) to toggle or momentary and therefore switching the 230Vac load momentarily or toggling ON/OFF.
You may also add a small tactile PCB mount momentary switch to make use of the ON/OFF functionality of this latch for manual user switching.

- - - Updated - - -

Part 3 for ANLEE:

Take great care in designing and making your PCB to keep the HOT (230Vac mains) and the COLD / SAFE side ( <12 Volts DC) separated by good Air Gaps for insulation as well as physical insulation between the primary and secondary sides of the Transformer.
This will reduce the risk of Dangerous voltages causing a shock and also protect the low voltage components from Damage by over voltage/current due to shorting or bridging of high and low voltage contacts.

Use a suitable case / enclosure to protect the user from the 230Vac Supply and if this is metal (such as brushed Aluminium) make sure that an earth connection is bolted to the inside of the case for safety and to prevent interference or damage to the computer interface cable.

 

[grantr37]

For Anlee:

Don't forget to add a 12 Volt Relay to your components list, I forgot to type that on here, you can now use an easily obtainable 12 volt relay

 

[annlee]

Thanks a lot!

seems too much for this I.T. Engineer, perhaps should hire an electronics engineer to handle all this

 

[DPG]

Hi. I would look into using a solid state relay. Much simpler and all handled in one 'black box device'. These take a low voltage DC in and can directly switch mains voltages. Simple and safe! Daz

 

[annlee]

Hi. I would look into using a solid state relay. Much simpler and all handled in one 'black box device'. These take a low voltage DC in and can directly switch mains voltages. Simple and safe! Daz

Honestly, I think it is better using another board that gives a 5V output (instead of IOIO with 3.3V), so can use directly a 230V/16A relay, right?

 

[DPG]

Would be simpler to use something like a 'CRYDOM - PF240D25 - SSR, 240VAC'. Specs are:

Load Current: 25A
Switching Mode: Zero Crossing
Blocking Voltage: 600V
Control Current Typ: 15mA
Control Voltage DC Max: 15V
Control Voltage DC Min: 3V
External Depth: 22.8mm
External Length / Height: 34.3mm
External Width: 43.2mm
Input Voltage: 3V DC to 15V DC
Isolation Voltage: 4kV
Load Current Max: 25A
Load Current Min: 0.06A
Load Current RMS Max: 25A
Load Voltage Range: 12V AC to 280V AC
Terminal Type: Through Hole

 

[annlee]

Would be simpler to use something like a 'CRYDOM - PF240D25 - SSR, 240VAC'. Specs are:

Load Current: 25A
Switching Mode: Zero Crossing
Blocking Voltage: 600V
Control Current Typ: 15mA
Control Voltage DC Max: 15V
Control Voltage DC Min: 3V
External Depth: 22.8mm
External Length / Height: 34.3mm
External Width: 43.2mm
Input Voltage: 3V DC to 15V DC
Isolation Voltage: 4kV
Load Current Max: 25A
Load Current Min: 0.06A
Load Current RMS Max: 25A
Load Voltage Range: 12V AC to 280V AC
Terminal Type: Through Hole

Is this solid state relay for IOIO board (3V output) or for the another one with output 5V?

 

[grantr37]

Hello Annlee
not a problem to build, I was assuming that you were an Electronics student and wanting help with a circuit design, I get asked a lot by Electronics students on different forums but they are usually looking to find out without telling that they are students as they don't want others back home to know that they are seeking help with college/university questions/projects...
you would be able to drive this circuit with a cheap USB I/O interface board (about 15 Euros) from any USB device running any platform/OS or RTOS /firmware just by setting the registers accordingly with code....could be run from a tablet, a laptop, an android phone or even something like a small dedicated board the likes of which are used to operate those video advertising signs that you see at the airport with TV commercials running on them....they are small at about 15Cm X 15Cm....
I take it that you have a few Electronics Engineers on your team? there is no way to avoid using Electronics for this as you will need to construct your own interface....let me know if you would like help with this for your team

 

[DPG]

This is a general purpose solid-state relay that is used in pretty much the same way as a traditional relay, but has the advantages of no moving parts, longer life, and wider input voltage range. It gives good isolation figures. Here is a link to it on Farnell's website: PF240D25 - CRYDOM - SSR, 240VAC | Farnell United Kingdom. Double-check the spec, but it looks like it would do what you want. There are probably cheaper ones available - this was the first one I found. Daz

 

[grantr37]

with modification and more expensive components (some surface mount SMD Device etc) this circuit could be designed to run entirely on battery power or even the small 5v 100mA rail provided by the USB device, although this would eat the batteries more quickly.......if you are looking for it to turn on and off an appliance for example without the Android device being plugged into a mains adapter and operating on internal batteries only....or you could even separate the device from the Android minicomputer using a Bluetooth module either internal or one of those tiny little low profile Bluetooth tranceivers that come with a wireless optical mouse plugged into the USB port (again a bit more expensive) but for USB alone it can be done really cheaply...

the separated Bluetooth receiver unit if used could be powered by an internal rechargeable battery and that could in turn be charged by using an inductive coil based charging circuit taking energy from the outer part of the supply cable without any physical connection...so it could be clipped onto the supply cable next to the appliance....as a plug adapter for instance...

 

[grantr37]

what device are you running the Google OS on? so I can know what hardware you would like to use, if it is for all Google Android OS hardware in general this is still easily done....

 

[annlee]

This is a general purpose solid-state relay that is used in pretty much the same way as a traditional relay, but has the advantages of no moving parts, longer life, and wider input voltage range. It gives good isolation figures. Here is a link to it on Farnell's website: PF240D25 - CRYDOM - SSR, 240VAC | Farnell United Kingdom. Double-check the spec, but it looks like it would do what you want. There are probably cheaper ones available - this was the first one I found. Daz

Thanks everyone, the system is meant to work buried (no fan required then + protection against water/dirt) 24/7/365 so batteries is not possible.

uhmmm even when I am not an expert, seems this device could work with the hardware as follows:

From 230v/16A cable = IOIO DC source (5V-15V) + (Android device <-USB-> IOIO board with 3.3V output) + PF240D25 relay + 230v/16A connector cable -> bulb



preferly max 15V source to feed IOIO?

I've found in Orange an "HTC Wildfire S" for 109 Eur, IOIO forums said this model works like a charm

grantr37, you seem to be all-an-expert so get ready if I log in again with newbie issues

 

[grantr37]

There are a few problems that may be encountered, the unit would need to be completely encapsulated in a resinous plastic, which during the factory curing/setting process would generate enough heat (Exothermal) to lift the surface mount components on the I/O card, in addition to this there would always be heat generated by the Integrated circuit chips on board that would become trapped and take extended periods to dissipate.....bonding a high efficiency heatsink would not work very well due to the fact that free air would not be available to allow for removal by convection, you would be relying on soil thermal coefficient, and any bonded metal heatsink would be subject to soil chemistry(corrosion)...
The thermal characteristics of the soil would also vary according to the weather and moisture content and components such as Resistors and capacitors (including non-electrolytic capacitor types such as coltan/tantalum) would be prone to failure in terms of both the physical characteristics altering with temperature differences and by permanent physical breakdown leading to loss of function..
I can't see any reason for burying a perfectly good mini computer device to control only one light fitting, it seems like an economically unproductive approach if this is for a business product?

which company do you work for?

 

[annlee]

There are a few problems that may be encountered, the unit would need to be completely encapsulated in a resinous plastic, which during the factory curing/setting process would generate enough heat (Exothermal) to lift the surface mount components on the I/O card, in addition to this there would always be heat generated by the Integrated circuit chips on board that would become trapped and take extended periods to dissipate.....bonding a high efficiency heatsink would not work very well due to the fact that free air would not be available to allow for removal by convection, you would be relying on soil thermal coefficient, and any bonded metal heatsink would be subject to soil chemistry(corrosion)...
The thermal characteristics of the soil would also vary according to the weather and moisture content and components such as Resistors and capacitors (including non-electrolytic capacitor types such as coltan/tantalum) would be prone to failure in terms of both the physical characteristics altering with temperature differences and by permanent physical breakdown leading to loss of function..
I can't see any reason for burying a perfectly good mini computer device to control only one light fitting, it seems like an economically unproductive approach if this is for a business product?

which company do you work for?

Great reply! I considered the heat problems but not so so... because its buried, but I think you are right
Since this system can work I am happy for now! the problem about heat, water, dirt... should be studied by a friend of mine, Mechanic Engineer and Expert in CAD to design the protective cover. Perhaps a 3V fan and/or even sinking in olive oil could refrigerate it properly

This system would be part of my PhD

 

[grantr37]

with a fan in a unit that would be by design intent covered in soil, this would serve no meaningful purpose, there is no free air for convection through expansion or available air for throughpass, the fan would also be subject to immediate mechanical stoppage and failure.
In addition encapsulation in any kind of oil would result in issues involving sealed (limited) thermal expansion which could result in possible rupture or strata charging, leading to chemical interaction with printed circuit tracks and components, the tracks could be lifted by warm oil or corroded by the nature of the oil chemistry, either of the two could lead to broken circuit board tracks and an open circuit, internal characteristic breakdown of the individual components could also occur, even when using mineral and synthetic oils blended for dielectric stability, this also applies to signal crosstalk where the liquid oil conducts between tracks and components, this can also cause issue with logic switching and signal debouncing...

 

[annlee]

with a fan in a unit that would be by design intent covered in soil, this would serve no meaningful purpose, there is no free air for convection through expansion or available air for throughpass, the fan would also be subject to immediate mechanical stoppage and failure.
In addition encapsulation in any kind of oil would result in issues involving sealed (limited) thermal expansion which could result in possible rupture or strata charging, leading to chemical interaction with printed circuit tracks and components, the tracks could be lifted by warm oil or corroded by the nature of the oil chemistry, either of the two could lead to broken circuit board tracks and an open circuit, internal characteristic breakdown of the individual components could also occur, even when using mineral and synthetic oils blended for dielectric stability, this also applies to signal crosstalk where the liquid oil conducts between tracks and components, this can also cause issue with logic switching and signal debouncing...

certainly, the heat is a big issue even when its buried, I think I do have to learn/read a lot yet

I was thinking about a ceramic-based jug cover around the sealed electronic devices + external metalic with a lock

This is how works the ceramic jug to refrigerate: Google Translate :blush2:

 

[DPG]

How warm is this thing going to get? Will the temperature exceed the maximum operating temperature of the components - you would probably be surprised how hot modern components can run at safely. Are liquid cooling and forced air cooling necessary? Daz

 

[annlee]

How warm is this thing going to get? Will the temperature exceed the maximum operating temperature of the components - you would probably be surprised how hot modern components can run at safely. Are liquid cooling and forced air cooling necessary? Daz

Good questions but I cant tell until I start the project :stuart:

 

[grantr37]

How warm is this thing going to get? Will the temperature exceed the maximum operating temperature of the components - you would probably be surprised how hot modern components can run at safely. Are liquid cooling and forced air cooling necessary? Daz

microcomputer hardware does not have a very good tolerance for heat, there are a few that are designed for low power operation and low thermal output, such as the Intel Atom processor, and a few ARM modules, other than that its down to RISC microprocessors ....

with overheating, it is a choice of continuous set-reset shutdown sequences or thermal runaway and burning out....

 

[annlee]

microcomputer hardware does not have a very good tolerance for heat, there are a few that are designed for low power operation and low thermal output, such as the Intel Atom processor, and a few ARM modules, other than that its down to RISC microprocessors ....

with overheating, it is a choice of continuous set-reset shutdown sequences or thermal runaway and burning out....

Hi there buddies, I asked Crydom about the PF240D25 relay heating specs and this is what they said:

Good afternoon,
The SSR you have selected is appropriated to your needs, only you have to be careful with the dissipation.If you use it without any forced air cooling, you can work with maximum 10 Amp at 25⁰C (see derating curve in datasheet)

If you have a forced air cooling, you can work up to 25 Amp, but you have to check the heatsink temperature: it must be lower than 100⁰C (you can measure it with a thermo-couple in the middle of the SSR, see picture below)


Regards.

I will be using a buried device at 16Amps, no air circulation but it has supposed thermal protection

perhaps should try to find another SSR or move forward with Crydom's one?

Thanks

 

[annlee]

Hi there buddies, I asked Crydom about the PF240D25 relay heating specs and this is what they said:



I will be using a buried device at 16Amps, no air circulation but it has supposed thermal protection

perhaps should try to find another SSR or move forward with Crydom's one?

Thanks

Latest news:

[FONT=sans-serif][SIZE=2]Hello,[/SIZE][/FONT][FONT=arial] [/FONT]
[FONT=sans-serif][SIZE=2]the PF240D25 cannot work at 16 Amp load without forced air cooling.[/SIZE][/FONT][FONT=arial] [/FONT]
[FONT=sans-serif][SIZE=2]Another option could be [B]UPD2425 [/B]([/SIZE][/FONT][URL="http://www.crydom.com/en/Products/Catalog/u_pd24.pdf"][FONT=sans-serif][SIZE=2]http://www.crydom.com/en/Products/Catalog/u_pd24.pdf[/SIZE][/FONT][/URL][FONT=sans-serif][SIZE=2]). [/SIZE][/FONT][FONT=arial][/FONT]
[FONT=sans-serif][SIZE=2]You must take care of the dissipation.
[/SIZE][/FONT][FONT=arial][/FONT]

[IMG]https://mail.google.com/mail/u/0/?ui=2&ik=37a18e3c0f&view=att&th=139d4bd5b529d8bb&attid=0.1&disp=emb&zw&atsh=1[/IMG][FONT=arial] [/FONT]

[FONT=sans-serif][SIZE=2]As you can see in the derating curve, you can work with 16A load at 30degreeC with a 5 C/W heatsink (you could use a metal panel for dissipation)[/SIZE][/FONT][FONT=arial] [/FONT]
[COLOR=#500050][FONT=arial]
[FONT=Arial][SIZE=2]Regards.[/SIZE][/FONT][/FONT][/COLOR]

So with this other SSR, the buried system would be under 30Cº if I use metal panel for dissipation + foam, I guess? :yinyang:

 

[KFH]

As has been said before burying an electronic device is a bad idea. I am sure people on here with more experience of cable joints than me will tell you that an underground fault is usually at the joint, and they are simple compared to an electronic device.

Part of good design is ease of maintenance, unless you are making disposable items, which most electronic devices appear to be these days but even then you would expect to be able to replace a component or assembly easily. Digging a hole to replace a device or even diagnose a failure is in my view not good design.

Draw up a list of pros and cons as part of your project to justify why it needs to be buried, it may even add a few points to your result.

 

[annlee]

As has been said before burying an electronic device is a bad idea. I am sure people on here with more experience of cable joints than me will tell you that an underground fault is usually at the joint, and they are simple compared to an electronic device.

Part of good design is ease of maintenance, unless you are making disposable items, which most electronic devices appear to be these days but even then you would expect to be able to replace a component or assembly easily. Digging a hole to replace a device or even diagnose a failure is in my view not good design.

Draw up a list of pros and cons as part of your project to justify why it needs to be buried, it may even add a few points to your result.

The reasons why it is buried: excellent protection against vandalism (important problem here), you dont need to dig if need to replace parts since it has a top with a lock plus a mechanism to extract it with ease, closer to the electricity cables where it is feeded, "low-cost" (one of the pillars of the project), tiny box, maintains lower temperature, it does not cause "impact" in the parade and it is discrete

The main cons are: worse refrigeration than cooling systems, humidity, not sure what other cons in comparison with its pros

:jester:

 

[KFH]

Ah, you do not appear to be burying it but putting it in an accessible underground chamber. That makes a difference to the cooling aspects and the accessibility for maintenance. The recommendations from others about using under rated components to minimise heat will probably still be valid. Will you get a reliable signal to activate the phone without an external aerial?

 

[annlee]

Ah, you do not appear to be burying it but putting it in an accessible underground chamber. That makes a difference to the cooling aspects and the accessibility for maintenance. The recommendations from others about using under rated components to minimise heat will probably still be valid. Will you get a reliable signal to activate the phone without an external aerial?

We need to test several covers and study which materials have in average better: hardness-heat insulation-signal allowance, however its too early stage to know that yet

 

[grantr37]

are there any questions that you have or would you like some help with your hardware design?

 

[annlee]

are there any questions that you have or would you like some help with your hardware design?

Thanks you are very kind,

I have a lot but if you dont mind I will rescue this thread when I receive the hardware and start working on it

Examples: I plan to add a typical green/red LED to show if its working or not, plus a proximity sensor to start the App

Please mods don't close this thread

 

[annlee]

Dear expert electricians, since the prototype must be "low-cost" I need to find cheap parts.

This SSR relay SSR-25DA 25A Solid State Relay - White - Worldwide Free Shipping - DX

seems to work for my specs: control of 3.3V, gives 16Amps/230V.

Furthermore, seems to work over 100ºC (sheet: http://www.fotek.com.tw/pdf/etc_33.pdf) does not even need a heat sink!!


Do you think this one can work or am I missing anything?

Thank You~

 

[ik_cw]

Thanks for all of the info. This is something I have needed a solution with as well. Cheers.

 

[annlee]

Thanks for all of the info. This is something I have needed a solution with as well. Cheers.

In few days I will have all the components and will update this,

it promises to be interesting...