Project files: A smaller mains controller…

What is it?
As mentioned a few weeks ago I’ve recently built another control board for switching a mains transformer with a low-voltage (latching) switch. This in a slightly different form factor so that if your application requires it, the board can be stacked with a matching standby-PSU and mains splitter and/or my passive softstart board. It is possible (just) to stack all three boards on top of each other in a 2U/80mm high enclosure or just two boards in a 50mm tall enclosure.

You can decide which standby voltage should be used by choosing the right relay in resistor values and in addition to using a latching switch for engaging the relay, you can also use a DC-voltage between app. 3-30V as the trigger. This input is isolated via an optocoupler and the trigger circuit only requires app. 15mA from the triggering device.

The matching standby PSU board uses the (by now) well-known IRM AC-DC power modules from Mean Well. There are two versions, one for the 3W module which is 100% outline-compatible with the control board and a version for the 5-10W modules where some of the connectors had to be shifted but the mounting holes still fit. The PSU board also provides a splitter-function to give two mains outputs.

How big are the boards?
All the boards are 2” x 2” (app. 51 x 51 mm) – the original theslowdiyer industry standard ™ 😀

What is the status of the boards?
These boards are v1.0 and they all work as expected.

Does it use any special/expensive/hard-to-find parts?
No.

Anything else I need to know?

  • The switch must be a latching type (meaning it stays in either on or off positions) and to turn the relay on you connect the switch so that the + voltage is connected to the switch pin. This turns on a transistor which switches the relay on.
  • The relay is rated for 5A inductive loads, so should be good for transformers up to around 1000VA at 230VAC (to give a bit of safety margin).
  • The optocoupler on the trigger input is fed from a constant-current source (CCS) made from an LM317L voltage regulator. If I was designing a commercial product this would probably be a sacking offence because it’s much more expensive than the alternatives, but for our purposes it works quite well 🙂
  • There are two LEDs on the control board, one to indicate the board is powered and one to indicate the relay is on.
  • The “ext” output is intended for us if you want to feed the unswitched standby voltage to some other circuit. There’s space for a bigger resistor here if you need to drop voltage for e.g. LEDs, but you can also jumper the resistor to just get the raw voltage (or leave the output if you don’t need it).
  • The mains connectors on the standby-PSU are marked as inputs and outputs, but in reality it doesn’t matter what you use as inputs and outputs.

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

Remember that these boards use mains voltage. Be careful when mounting and handling them!

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Project files: ATtiny-based power delay

As the PCBs for my next ATtiny-based designs have landed over the weekend and I am back from my holidays, now seems to be an appropriate time to post this 🙂

What is it?
It’s my ATtiny85-based power delay controller which can be used for speaker protection etc. as described here. In addition to the controller board itself are also a couple of relay boards to do the actual signal switching. One board is stereo and based on 10A relays, the other is mono and based on a 30A relay.

The controller board includes an on-board 5V regulator, an LED coupled directly to the ATtiny to indicate when the relay is engaged (or another purpose) and two FET-switched outputs. The last two ATtiny I/O pins can be used to trigger the chip with buttons, sensors etc. which gives tremendous versatility.

How big are the boards?
All three boards are my “industry-standard” 2”x2” (app. 51 x 51 mm.) in size, meaning they can be stacked on top of each other if needed.

What is the status of the boards?
All three boards are version 1.0 and the prototype boards looked and worked as expected.

Does it use any special/expensive/hard-to-find parts?
Nothing serious this time either 🙂

  • The small heat sink for the regulator is a Fischer type SK95 with an M3 hole in the bottom, but if you’re having trouble finding this there should be plenty of other small heat sinks that will fit. In any case, the heat sink isn’t always required, it depends on your input voltage and current draw from the 5V line.
  • The relays are standard types, either Omron G5LE (small board) or Omron G8P (large board). I’ve quoted Omron part numbers to give you something to go on, but there should be plenty of identical replacements from other manufacturers available.

Anything else I need to know?

  • The intention is that the ATtiny chip should be programmed using the Arduino IDE. That means you need to have either a dedicated programming shield for ATtinys or wire up the chip to an Arduino board that is used as an ISP. You also need to have the ATtiny cores installed in your Arduino IDE (see explanation here) and you have to burn the Arduino bootloader onto the ATtiny yourself before filling it with the actual program.
  • For programming, I highly recommend something with a ZIF-socket because it will make the whole thing much easier. I’ve got one of these on order (which recently came back in stock) because that looks brilliant, but there are shields on ebay that can be used as well. I’ve been working with this one so far and it works well, but of course you need a dedicated Arduino board to run it.
  • As you can see from the schematic, the intention is that the controller board is fed from a higher voltage (9-24V) than the ATTiny requires, in order to be able to use relays that draw less current. The onboard regulator will provide the 5V that the ATtiny requires.  If you are using the big mono relay boards, be aware that the worst-case power draw for these is around 1.2W each. This means that if you are using a pair of 9-12V relays here you’ll need to be sure that your power supply can handle that.
  • The second output is intended as just that – a secondary switch – but since it’s connected to one of the ATtiny pins that provide a PWM-output, you could probably do something clever and use this for controlling a variable-speed fan fed from the same voltage as the relays. If anyone does that I would love to steal, ehm…. borrow your code 😀
  • Although the relay boards have on-board protection diodes across the coils, there is also space for optional SMD diodes on the bottom of the controller PCB. Use these if you’re driving off-board relays etc.
  • There is a sample sketch included in the download file, but please don’t laugh (too loudly) at my pitiful attempts to code – it’s just an example 🙂

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

Most of the complexity here is around the coding. There are tons of links available around the web for how to use ATtinys with Arduino, so I’ll not list them here. Start from the link to the official Arduino page and then do your own search from there.

Project files: Universal selectors (part 2)

This is the second part of my ”universal selector” series (the first one is here). This post includes the control boards designed to match the selector boards from the first post.

What is it?
Control boards for the relay-based selectors. The download file consists of three designs:

  • A “push-button” input selector based on the 4017 counter IC. This is more or less the same circuit as the selector-part of the ICE-int PCB.
  • A PCB for a rotary-switch based selector.
  • A simple PCB for a 4-LED input indicator that can be used with the above boards.

The last two boards are also suitable as “companions” for the ICE-int board.

How big are the boards?
The board sizes are as follows:

  • The 4017 button switch board measures 1.35″ x 1.35″ (app. 34 x 34 mm.)
  • The rotary switch board measures 2.0″ x 1.25″ (app. 51 x 32 mm.)
  • The LED indicator board measures 0.6″ x 1.3″ (app. 15 x 33 mm.)

What is the status of the boards?
The switch PCBs are both v1.5 because they are existing designs that I have revised to match the standard pinout for the selector boards. The LED PCB is v1.0 because I only realised I needed it after putting everything else together 😉

Does it use any special/expensive/hard-to-find parts?
Nothing that’s worthy of any real concern: The rotary switch is a standard 3pole/4position rotary switch which is made by many different manufacturers (Lorlin, C&K etc.). I’ve tried a few and some seem to fit the PCB a little better than others but with a bit of lead-bending they should all work.

Anything else I need to know?
Some quick notes:

  • The connections between the boards carry power as well so under normal circumstances these boards do not need their own PSU (power is applied via the relay board).
  • 4017 PCB: This is basically the control circuit from the ICE-int PCB, separated from its companions and “spiced up” a bit. The selection is performed by operating the 4017 as a counter, triggered via a debounced mechanical switch. The “spice” consists mostly of a second control input via a PC817 optocoupler which can be connected to a microcontroller port if that suits the application better than a manual switch. The optocoupler then acts as a level shifter making it independent of the relay voltage.
    Most versions of the 4017 will run on power from app. 3V-18V, so as long as relay voltages are within that range it should be fine. For 24V relays, there is a resistor on the board that can be used to drop the supply voltage to within a safe range for the 4017. For 48V relays this solution isn’t really practical and the rotary switch selector should be used instead.
  • Switch board: The switch PCB uses two of the three decks of the switch. One side can be powered externally so it is e.g. possible to use 24V/48V relays and then a separate supply for the LED board which prevents having to drop a lot of power in the LED resistors. If you want to connect the two sides and use a single supply from the relay board, use the jumpers marked JG (for GND) and JV (for V+).
  • LED-board: The “normal” board has separate resistors for each LED so you can use different LED colours if needed. A simpler version with just one resistor is also included. The two boards are mechanically identical and made so they can be mounted vertically on a 1U enclosure front panel. The LEDs are spaced 0.35″ (9mm) apart and the mounting holes are 1″ (25.4 mm.) apart. The offset between the center lines of the LEDs and the center line for the mounting holes is 0.275″ (7mm.).

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

Project files: Universal selectors (part 1)

This is the first in a series of posts for relay-based input (or output) selector boards made to be as universal as I could reasonably make them. This is part one, the selector boards themselves. Part 2 (which is coming shortly) includes the matching control boards (button-based and rotary switch) and an LED indicator board. There might eventually be a part 3 (and 4) as well to cover some additional variants and accessories.

What is it?
A relay-based selector boards with four single-ended inputs (or outputs). There are four board sizes, distinguished mainly (well, only…) by the spacing between the relays and input connectors:

  • Size S: Input spacing 0.5” (12.7 mm). This is the minimum size I could reasonably make the board. The spacing is smaller than typical RCAs, but would be suitable if you are using different connectors e.g. mini-jacks or if you need to keep the selector board separated and run longer wires to the inputs. This is the same basic size as the ICE-int board.
  • Size M: Input spacing 0.75″ (19mm). This is the spacing of many integrated and/or low-cost RCA sockets.
  • Size L: Input spacing 0.95″ (24.1 mm). This is the standard size board size which gives a bit more space between connectors and thus allows using better-quality “premium” RCA sockets. It is also the biggest board that can be made to fit inside a 5×10 cm limit as imposed by many board manufacturers.
  • Size XL: Input spacing 1.1″ (28mm). This is the standard spacing for Neutrik D-series RCAs/XLRs and so the one that is best suited if you want to stack two selector boards for balanced inputs.

Note: There is no functional difference between these boards. The only reason for using a specific version would be to make the wiring between the board and the connectors as neat as possible.

All boards share the following features:

  • Standard “2-form-C” relays are used (Takamisawa RY-xxW series, Omron G5V-2 series or similar). Depending on how the boards are controlled, relay voltages between 3 and 48VDC are possible.
  • Universal in/out connectors.
  • Power connectors at both ends of the board.
  • Stackable for balanced configurations (or if you need more than 4 inputs)
  • Space for optional termination resistors on the bottom of the board (1206 SMD footprint), so that unused sources see a finite load instead of an open connection.

How big are the boards?
The board sizes are as follows:

  • Size S: 2.6” x 2.0” (app. 66 x 51 mm.)
  • Size M: 3.35” x 2.0” (app. 85 x 51 mm.)
  • Size L: 3.95” x 2.0” (app. 100 x 51 mm.)
  • Size XL: 4.4” x 2.0” (app. 112 x 51 mm.)

What is the status of the boards?
All the boards are labelled v2.5. I originally made a layout much like this back around 2006-2007 which I used as a starting point. Version 2.0 was the first attempt at cleaning up these and introducing more versions. Version 2.5 is because I’ve more recently cleaned up the silkscreen and standardised the control connector pinning to match the switch boards.
These boards were developed separately but should now be completely aligned and integrate without issues. I’ve prototyped v2.0 of all of them except the XL version where I have made the v2.5-version (as shown).

Does it use any special/expensive/hard-to-find parts?
None. The relays can be Takamisawa RY-xxWs or any one of the many similar parts. You should be able to buy these from ebay and any other source.

Anything else I need to know?
Some quick FAQs with answers:

  • Q: Can I use the boards to switch outputs instead of inputs?
    A: Yes, however in order to have more than one relay active at a time you will have to do the switching in a different way than what I have done.
  • Q: Can I use the boards to switch headphones?
    A: Probably. I haven’t tried it, but I expect it would work. Same caveat as above on multiple outputs though.
  • Q: Can I use the boards to switch digital/coax sources?
    A: Well, it’s definitely not designed for that purpose but better dacs might be able to survive the signal degradation. By all means try it, but no guarantees 🙂
  • Q: When do I need to use the termination resistors?
    A: Not sure actually. Some sources are reportedly not happy with a no-load condition and in the spirit of versatility I decided to cater for that eventuality as well. If you do fit the resistors they will also serve as a discharge path for any source that has a capacitor-coupled output which might help. Values between 10k and 100k should be fine here.

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

Project files: ICEpower integrated amp board

What is it?
The project files for the “all-in-one” (nearly…) PCB for making integrated ICEpower amps shown in the previous post.

How big are the boards?
The board measures 2.65″ x 3.15″ (app. 67 x 80 mm.).

What is the status of the boards?
The board is version 2.1. As mentioned, it’s an old design that I have revised and updated to give it the 2.x version number. I’ve built my prototype on a v2.0 board and made some minor tweaks to that before publishing.
The changes in v2.1. are mostly mechanical (too little space for the input connectors etc.) and then minor touch-ups to the silk screen.

Does it use any special/expensive/hard-to-find parts?
No. The overall circuit is quite simple and only a few parts require a bit of attention.

  • The relays are standard mid-sized “2 form C” contact types. If you’re buying from scratch I’d recommend the Takamisawa RY-12W type, but there are app. 1 million equivalents with similar specs and footprint, so you may be able to get good surplus deals as well :). The coil voltage must be 12V.
  • The voltage regulators are standard 7812/7912 types but as they are mounted very close together I recommend the fully-insulated versions. I prefer the ones made by NJR as opposed to ST because the ST-ones seem to behave a bit strangely sometimes (and yes, I might be imagining this…).
  • See BoM-file for description of other parts and values.

Anything else I need to know?
A few things:

  • The on-board parts draw no current from the negative PSU rail. If you’re not using any external circuitry you can omit the negative rail (regulator etc.). If you build it anyway and get strange results, note that some regulators do not like a “no-load” condition and will give an weird unregulated output if not loaded. You can solder a 1-3k resistor on the bottom if you want for added peace of mind.
  • ASP/ASC-usage: It’s possible to use the board with ICEpower ASC and ASP modules. As these include a regulated +/- 12V AUX supply, you should jumper the regulators and the input resistors. The capacitors and remaining components can be left in.
  • Mute-header: The Mute-header simply brings the two pins required for the module’s mute or standby pins to work to a header at the from of the board to simplify wiring. Refer to the datasheet for the respective modules for details on how to use this, but in general you can switch using a mechanical switch.
  • Heat sinking: There is no heat sinking of the regulators as standard. With a simple preamp and no additional load this should not be necessary, but if you want to draw more power then use a small bit of metal as the heat sink. There is not much space in either direction, so using insulated regulators will once again be an advantage.
  • If you prefer a manual input switch, the board is just about ready and will be presented as part of another project post in a few weeks 🙂

Downloads:
Download design files here

Related information:
Please read the FAQs in the original post as well. The picture below shows my “in progress” prototype amp with the Minipre and a 50ASX-module and gives an idea of the expected layout.

Note: Always read the “intro post” for additional important information about my designs.

ice-int-wip

 

Project files: A PGA231x Volume Control

What is it?
A “digital” volume control based on the well-known PGA2310/PGA2311 ICs from TI. These aren’t actually digital, but just digitally-controlled resistor attenuators integrated on an IC – which doesn’t really matter anyway.

As is often the case, there are two board versions: One is a “normal” stereo version with a single PGA chip onboard, the other is a balanced/multichannel version that has two chips onboard (for balanced setups) and the possibility to daisy-chain more boards (for multi-channel systems). The boards are intended to be controlled from an Arduino or a similar microcontroller via an SPI-interface. I haven’t included any software in the download file, but there should be plenty of examples online that shows how to do this integration (especially for the Arduino).

As even the not so keen-eyed observer will notice, this isn’t a new layout. I recently realised I didn’t post these before and as the project they were meant for died somewhere along the way I am not sure I’ll ever pick these up again (at least not within the foreseeable future).

Note: I had some minor noise-issues with the boards. As I never got beyond bench-testing, the noise could be from any number of sources other than the layout (my shoddy test wiring, poor PSU, the poor USB supply that I used for the arduino etc.). This means that although the PCB layout is made according to (what I believe are) the TI recommendations for the PGA231x, I cannot guarantee that the finished board will perform 100% flawlessly without tweaks.

How big are the boards?
The stereo board measures 2.525” x 1.6” (app. 64 x 41 mm.)
The balanced board measures 2.525” x 2.65” (app. 64 x 67 mm.)

What is the status of the boards?
The boards are v1.0, meaning finished and technically working as I expected. Please do note the caveat above around noise though.

Does it use any special/expensive/hard-to-find parts?
None, really.

Anything else I need to know?

  • There are plenty of examples online for interfacing the PGA ICs with Arduino and other microcontrollers – do a search of diyaudio and the Arduino forums for a start.
  • The PGA chip wants to be driven from a low-impedance load and the input buffer sees to that – use whatever dual opamp you prefer here. If you don’t have a favourite already, I’d recommend the LME49720/LM4562 as long as they are available:) The PGA has a buffer of its own on the output and it is spec’ed to drive loads down to 600 ohms which should mean that all common configurations are catered for.

Downloads:
Download design files here

EDIT 23/4-2017: In response to the reader comments below, here is a basic BoM for the single board. As the dual-board is basically two sections of the same circuit, you should be able to work out the BoM for that yourself 🙂

Related information:
Note: Always read the “intro post” for additional important information about my designs.

Please also refer to the data sheet for the PGA2310 for information about controlling the chip etc.

Project files: Mains controller with offboard relay

What is it?
A version of my Standby-PSU & controller for applications that need to switch very high (or very low) currents, switch multiple relays or simply prefers to use an offboard relay, be it mechanical or SSR. A couple of matching PCBs for relays and a soft start will follow very shortly, I just need to process the pictures and finish the write-up. This is basically the same circuit as the “v1.5” of the standbyPSU (found here) without the onboard SSR.

How big are the boards?
This version measures 3.2″ x 1.875″ (app. 81 x 48mm) – so just a little smaller than the v1.5.

What is the status of the boards?
This board is v1.0 and it works as expected – not entirely surprising given that it is mostly identical to the v1.5 circuit which also worked well.

Does it use any special/expensive/hard-to-find parts?
No.

Anything else I need to know?
Note that big mechanical relays tend to draw a lot of power, so there might not be that much power left over to power anything else. As an example, the relay board that I will post later draws app. 1.2W. Throw in a couple of LEDs and the losses in the transformer, and there isn’t actually that much left over from the 2.5-3VA transformers that are the maximum that will fit on the board. You can of course use the controller to control a separate standby-PSU as well.
If you want to use an SSR, then be aware that they can be a bit tricky to work with and some attention must be paid to minimum load etc. I can recommend reading this document from Omron that explains a lot.

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

You can also read the other posts on this controller design for information.

Project files: Relay-based attenuator

What is it?
This is the board files for my relay attenuator described here.

How big are the boards?
The board measures 3.85″ x 2.4″ (app. 98 x 61 mm.)

What is the status of the boards?
This board is version 1.0. It has been built and tested and I haven’t really found it necessary to make any changes based on the prototype.

Does it use any special/expensive/hard-to-find parts?
Not really 🙂

  • The relays must be the specified Omron G6K 5V version and the ULN and MCP ICs should be in the right packages (SO-IC). All these parts should be available from the usual sources, i.e. Reichelt in Europe and Mouser/Digikey in the US and worldwide.
  • The resistors should be 1% tolerance or better and some of the values are from the E96 range which might not be available in the shop around the corner but should be available from most of the mail order companies.

Anything else I need to know?

  • Refer to the original build article (link) for some additional information and helpful links to Arduino code samples etc.

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

relayattenuator-1

Project files: SLA battery charger

What is it?
For one of my work-in-progress builds I needed a simple charging circuit for an SLA (sealed lead-acid) 12V battery. So, good excuse for another project 🙂

Compared to the Li-Ion or LIPo-batteries used in most applications today, charging an SLA is extremely simple. You use a fixed voltage and then set a limited charge current of around 1/10C or a trickle-charge current of around 1/20C and off you go. (“C” is the nominal capacity of the battery, so 1/10C for a 7Ah battery is 700mA).

A bit of searching online turned up a few suggestions but one appealed more to me than the others, mainly because of its simplicity. The circuit is built around the L200 voltage regulator which features programmable voltage- and current limits, which is exactly what this application calls for. I believe the original circuit is from Elektor, but I am unable to find it so I relied on the web versions here and here instead.

How big are the boards?
The board measures 1.95″ x 1.6″ (app. 50 x 41 mm) without the heat sink.

What is the status of the boards?
The published version of the board is 1.1. Changes from the prototype v1.0 that I built are fixes for some misprinted LED-labels (doh!) and some minor touch-ups to the silkscreen – nothing major.

Does it use any special/expensive/hard-to-find parts?
Not really. Just be a bit careful checking component dimensions against board footprints because there isn’t much space left over.

Anything else I need to know?

  • The PCB is meant for currents smaller than 1A due to the limitations of the rectifier and protection diodes. With a bit of searching it is possible to get 2A components that fit, however whether this is a good idea from a thermal POV remains to be seen.
  • The component values are normally meant for 12V batteries (and a 13.8V charging voltage). A few of the articles have component values for 6V battery use as well, but if anyone can easily recalculate for 24V (2 batteries in series) please let me know.
  • The L200 regulator must be heat sinked, but how much depends on charging current and input/output voltages. The one on my picture was the only one I had with pre-drilled holes, so don’t take that as a recommendation/indication in any way 🙂
  • Although not shown, fuses should always be used in series with the charging battery. An SLA battery is capable of some truly terrifying short-circuit currents, so there should always be a fuse to protect the circuit from damage.

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.

Project files: Mains controller v1.5

What is it?
As promised in the original post, an update of the Mainscontroller design to v1.5.

This is the transformer-based version 1.1 which I have tweaked a bit. There aren’t really any functional changes but I cleaned up the layout a little and included some things from the rev. 2.0 such as a “”proper” terminal block for the switched DC output. Also, two versions are included, one with an onboard fuse and a single output connector, the other without the fuse and with two parallel outputs instead. The holes are compatible between the versions and all parts except the output connectors and fuse holder are identical between the two versions.

There are some minor tweaks to the included BoM as well, mainly the addition of values for a 9V option but also tweaks to some resistor values for more consistent operating points between the versions.

How big are the boards?
Both board versions measure 3.7″ x 1.875″ (app. 94 x 48mm) – the same as the older v1.1.

What is the status of the boards?
As mentioned, this is v1.5 of an already tested design. I have built one copy of the single-output version and it works as expected.

Does it use any special/expensive/hard-to-find parts?
Compared to the original v1.1, no.

Anything else I need to know?
If you’ve read the comments in the original post, then no 🙂

Downloads:
Download design files here

Related information:
Note: Always read the “intro post” for additional important information about my designs.