electronics – Page 5 – Richard Mudhar

Olympus LS10 and LS14 DIY wired remote control

tl;dr – the schematic

Olympus LS10 (and LS14) wired remote schematic

A new approach to a timed recorder

For the last year or so I’ve been trying to make an timed start recorder using a Raspberry Pi and the Wolfson/Cirrus audio card. I was able to make it work, but never eliminate some rattiness in terms of overruns on record – I confess I couldn’t hear them, but it didn’t give me a good feeling. Then I added up the costs –

£25 – Cirrus Audio card
£27 – Raspberry Pi B+£10 – case and odds and sods to make it work
£20 – PCB, time and bits to make a preamp to get from mic to line level

so I’m looking at £80 to get off the ground, and that gives me a seriously power-hungry SD audio recorder, although I can use a timer to save the power drain for active service.

Alternatively, if I could crack the remote control for them I could go on ebay and get a secondhand Olympus LS10, or one of the similar models (LS-5, LS-11, LS-12, LS-14) and use my own LS10 to start with. I can feed a mic straight into the LS10, no extra preamp required and the audio spec is good.

Reverse engineering the Olympus remote control protocol

This cost me £90 on ebay, and it turned out I didn’t need it. You get the info for free, but then I got a natty nearly new LS-14 with an RS30 remote control, so I’m not too unhappy. Unfortunately the RS30 doesn’t work with my Olympus LS10, don’t know why. I’d have been hacked off if I’d just got the RS30¹. Works a treat with the LS14 it came with, on their own a RS30 seems to go for £50, so I got an okay deal.

Google first – I owe dashanna of the naturerecordists’ list for inspiration, I vaguely recall seeing that post go through on the list. Their solution is this

1610_dashanna

The connector is an evil little 2.5mm four-pole jack, and these are a bear to solder

nasty connectors to solder, though easier when you realise you only need t wire to two parts. You can pick up 3.3V on the tip, which may be of use... — nasty connectors to solder, though easier when you realise you only need to wire two parts. You can pick up 3.3V on the tip, which may be of use…

I can’t help wondering if life would be easier using a three-pole jack, since only sleeve and ring are needed. Now I didn’t like that battery in dashanna’s version – I mean who the heck would make a wired remote for a machine offering you a 3.3V supply on the tip of the plug and demand you go fit a battery in your remote? It’s just not a clean engineering solution at all. But apparently it works.

So I rigged the cable in series with the RS30 and sniffed the signals. Of the TRRS the tip had 3.3V, the second ring seemed open circuit, the first ring had the wanted signal and the sleeve was ground. Presumably the IR receiver and LED driver are powered off the 3.3V on tip. The signal on the first ring rests high at 3.3V.

Record is this funny little signal, 100ms at about 1.5V followed by a low

Stop is this signal, pull to ground for 100ms

In practice you can ignore the second pulse. For all I know it could be an ack back to the receiver to light the LED. I tried using a couple of diodes to pull the signal down to 1.2V but that didn’t initialise record. I then figured this is one of those analogue resistor chain remotes, so I look for what resistor would give me ~1.5V. Turns out if you replace the 1.5V battery in dashanna’s schematic with 100k you get about 1.5V and the recorder starts recording. You don’t need the second pulse at all, and the debouncing seems to be done in the recorder, it takes a little while, up to about half a second to start recording. I guess that means inside the recorder there’s a 100k resistor to the 3.3V rail in series with the first ring.

That works with both the LS 10 and the new LS14, although the RS30 only works with the LS14. So now all I need do is mod the timer to pull down a couple of pins, one through 100k. If I make the stop command the open-drain pin to ring and the rec command a normal pin resting High via 100k to ring, and pull the relevant pin down for 100ms I should be good to go.

I’ve just got onto the Olympus RS30 website and if you scroll through the models that is compatible with it includes the LS-3, LS-5, LS-11, LS-12, LS14, LS-20M, LS100 so perhaps my LS10 was never compatible with it and Olympus have changed their mind since writing the LS10 manual which says on p65 “Exclusive remote control RS30W (scheduled for Spring 2008)” ↩

How to use an external GPS with a smartphone

The best GPS for a Brit searching for prehistoric stones is a GPS which has OS maps built in.

The trouble with these is the sticker shock, you’re looking at about £300-400, which is still a bit stiff. If you start with nothing, it’s probably still the best way, and you will undoubtedly get a better moving map experience, particularly with a GPS including an electronic compass, which will orient the map correctly for you.

I had a smartphone and Viewranger. I’d bought the Landranger 1:50k set of OS maps on viewranger for about £70 – once you buy digital mapping you’re locked into that provider unless you want to pay up again.

Smartphone GPS is awful and power-hungry

The big problem with a smartphone is that GPS performance is dreadful. Quite how dreadful I hadn’t realised until I got out on Dartmoor and tried to use Viewranger, which made no attempt made to track current position.Well, pretty much until I was on my way back to the start point. I had a paper map anyway, although the smartphone version was easier to control in the wind!

A-GPS doesn't help you here — A-GPS doesn’t help you here

The problem with a smartphone GPS is that by design it will fail you when you need it most, on a featureless moor with no signal. It is new-born each time you start it up. Rather than maintaining the ephemeris (knowing where to look for the satellites) when the phone is off, smartphones use A-GPS – getting the rough location from the network connection and using this to simulate the ephemeris.

Which is OK in towns, and no good to man nor beast in rural areas, because there’s no network connection. So you get to do a cold start of the GPS which can take over half an hour. No fun at all when you are out on Dartmoor. Even in towns the performance of smartphone GPS is dire, compared to a handheld GPS, as I found out looking for birds. Plus it’s power-hungry – running about 43mA @ 5V with continuous GPS on, compared to 25mA with a BT GPS.

Go for a separate Bluetooth GPS

A secondhand CoPilot GPS3 The default Bluettoh code for one of these is 0183 (from NMEA 0183 protocol, I guess) — A secondhand CoPilot BTGPS3, 2003 vintage
The default Bluetooth code for one of these is 0183 (from NMEA 0183 protocol, I guess)

and use an app to get the location signal into the phone, something like Bluetooth GPS to set this as a mock location provider. Then shut off the internal GPS to save power. Start the hardware, then start the app before starting Viewranger, and everything will work better than before. The CoPilot battery is good for six hours, ebay has many more modern equivalents which probably have better battery life. You can save more smartphone power in the sticks by putting the phone into flight mode and specifically re-enabling Bluetooth, this shuts down the power-hungry wifi and phone data systems. Plus it stops Google knowing where you are in real time 😉

I still hanker after a Garmin GPSMAP64 because while this sorts out the poor GPS performance, it is hard to see the smartphone display outdoors, even under a wide overcast sky, and impossible with sunlight falling on it. Nevertheless, the smartphone app is a lot more practical now.

Ciseco – WirelessThings goes to the wall

Sad day, I used their RF modules for farm telemetry and they were great products at a good price. I have a fair stock of their XRF and RFu micros and bought a few of the latter and a bunch of boards in their closing down sale. But I’m sorry to see them go, and support and data are going to be nonexistent now. London Stock Exchange RNS announcement

They’re still on GitHub as Ciseco, the original company, though I guess how long that will last is questionable

There is basic info on the XRF command set on the wayback machine version of the old Ciseco site

Launchpad on Github

Timed Audio Field Recorder with a Raspberry Pi Cirrus Logic Audio Card

The problem is still the same as it was this time last year – the birds get up before I do in the Spring and I can only be one place at a time. Automatic recording devices let me scout locations in parallel.

A timed field recorder needs to be cheap, because somebody might nick it, it needs to be weather-resistant because it’ll be stuck outside, and it needs to be low-power, because 13A mains sockets are rare outside. Oh and it needs to be standalone, and not part of some cloud, because mobile Internet is ratty and expensive.

tl;dr the hardware performance is good but software support is dire

You can make this work but it isn’t fun at all. If you can use something like a USB stereo audio in board then do that rather than use this Cirrus Logic Audio Card, particularly if you have mains power available. I like the Behringer UCA202 and it works with the Pi.

A Raspberry Pi and A Wolfson audio card sort of fitted the bill, but the Wolfson Audio card is no more. I say sort of, because I’m still looking at about £70 for a Pi¹, the audio card and enough odds and sods to power it. You can buy a Zoom H1 for about £80, although there’s still a bit more cost in powering it for long times, keeping the water out and making up some gizmo to pretend to be you pressing the big rec record button early in the morning.

But with the Pi I get to drive the recorder via cron and ssh, and transfer the files via the internet or mobile data in some places. Even if I don’t get a case, though they are to be had for the Pi/CL Audio card combination…

Continue reading “Timed Audio Field Recorder with a Raspberry Pi Cirrus Logic Audio Card”

Making a fake Chinese Wattsup 12V power meter less dangerous

You can buy a pukka Wattsup meter from RC Electronics for $60. That’s just too dear for me, I want to be able to apply a few of these in various places, so I go with the cheap fake Ebay version for £5.99 🙂 At the time I didn’t realise it was a cheap fake Wattsup, it was simply billed as Watt Meter

It duly arrived from some joint in Shenzhen and it wasn’t hard to see that quality control left something to be desired. But hey, whaddya expect for £6? I couldn’t source the LCD display and box for £6!

Chinese suppliers don’t actually have to deliver reliability at these low prices because the cost of sending the product back to China for a refund is higher than writing off the goods. Since I’m prepared to fix the odd part I’m happy to take the risk. It didn’t seem to be a good idea to apply a 12V car battery to this sucker as is, without some investigation. Plus having the display centred is a nice touch…

Hmm, nothing to centre the boards. Other than that, looks okay, except for the exposed positive solder joint in the main battery 12V line Insulated from the case by the blue anodising and now’t else. At least the LCD contacts are pushed away from the metal by some foam. The LCD groundplane ends just shy of the edge of the board so it may not short on the box, but it still seems a risky business to risk having the box at +12V potential when the anodising gets scraped through. Most 12V systems assume exposed metalwork is either isolated or connected to the negative terminal. I don’t feel that lucky as to go around with a +12V exposed metal box, so I got some of that pressed card (plastic can easily melt if it gets hot) and put it in inside the box, to at least give me an extra layer. I do see the wisdom of RC electronics using a plastic case, but then an 80% discount speaks a language of its own. How do I know it’s a fake Wattsup? Continue reading “Making a fake Chinese Wattsup 12V power meter less dangerous”

12V LED Sound to Light or Color Organ

I made a couple of sound to light units at school and university many years ago.

1977 - around the time when I started making my first sound to light — 1977 – around the time when I started making my first sound to light

Not much has changed about the technology, but on the display side LEDs are made for these – not only do we now have the chance of running the system at 12 or 24 V but we can avoid all the fun and games with mains triacs and pulse transformers – I got several mains shocks in those days, because while I optoisolated the main circuit from the triacs using MOC3020 opto-triacs the metal tabs on the triacs were live via the lamps, and on the same circuit board…

Now the Chinese make these things to drive LEDs by the millions on ebay and Amazon, and the sound to light is usually an add-on to a box designed to set moodlighting by colour with a remote control. And the sound to light function is crap on the two I’ve tested – I sent one back to Amazon because it was so dreadful it wasn’t worth the £12, although the cheaper Chinese device I have the light chase mode is acceptable.

Lancaster's original article — Lancaster’s original article showing the filter design

There’s not much that has changed about the filtering from Don Lancaster’s 1970s article – sure we can use opamps or DSP but the essentials are still the same half a century later. I want to use proportional PWM control with the LEDs. Continue reading “12V LED Sound to Light or Color Organ”

GPS serial receiver for Kenwood TH-D7

press the pos button while GPS data is running at it will show you the locator,and lat/long, the degree and decimal points flash on reception. With an unlocked GPS it is lat/long of 0

This project is to make something that used to be common – a GPS receiver with serial data output. Modern APRS handhelds like the THD72 have GPS on board, but my Kenwood TH-D7 is from the turn of the century and doesn’t have onboard GPS. I used to pipe the output of a handheld GPS into the serial port. That worked fine, but in the field it’s a drag to use a handheld GPS tethered to a rig. Every time you want to put something down or set the rucksack down you end up with a knitting session on the cables. This is why they invented Bluetooth, and one option I considered was running a little Bluetooth receiver to a Copilot BT GPS. Trouble with the Copilot is how do you recharge it in the field, and I need to pick off power from somewhere to run the Bluetooth receiver. So I still get cables to the rig and another battery to manage 🙁

Most handheld GPS receivers like my Garmin Vista HCx have moved on to USB serial interfaces now, whereas the 1990s vintage Kenwood TH-D7e uses 4800-n-8-1 RS232, which is what GPS units chucked out in those days. Early THD7s had a problem reading the serial stream since NMEA 0183.3 superseded 0183.2 for the reasons described in the Potator article. I assumed my unit was one of these, so I constructed the Potator, but while the rig worked through it, it also worked without it, so I was lucky and dispensed with that 🙂

Continue reading “GPS serial receiver for Kenwood TH-D7”

A Ravpower USB iSmart battery doesn’t like low loads

I have one of these Ravpower iSmart USB batteries, and it works a treat when used as the manufacturer intended – to power a mobile phone or an iPod (4th gen touch in my case). No complaints whatsoever.

I constructed a remote GPS module with MAX232 RS232 chip, and all this wants to run off 5V – the MAX232 is specced at 4.5V to 5.5V, the GPS is probably more tolerant. So the obvious thing to do is to cut off a USB cable, use the USB A plug and wire the power to my device from this. No need for a regulator, job done, and indeed the GPS fires up. Dandy. No need for 5V regulators, no need to mess about with undervolt cutoff, 5V power straight out of the box, what’s not to like?

An intelligently managed battery

The USB battery gives me a USB chargeable device and integrated power management, you can’t overcharge these or run them flat, and as someone who has just trashed a LiPo battery by leaving it connected overnight and flattening it, I appreciate that thought. Until I find out that

iSmart is too darn smart

and decides my device isn’t drawing enough power and pulls the plug after a couple of minutes. Damn. My GPS draws a hefty 50-60mA, depending on whether the unbelievably bright LED the Chinese makers decided to fit is on or not.

Continue reading “A Ravpower USB iSmart battery doesn’t like low loads”

Revisiting Amateur Radio

I took my Radio Amateur’s Exam (RAE) in 1978 – I’d been interested in electronics as a child but I was never going to be able to afford any gear, I thought a technical interest would add a little bit of colour to my application to do Physics at Imperial College. My grandfather had been a radio amateur and he gave me an old homebrew crystalled 2m AM rig. But when I fired it up and my Physics teacher who was a radio ham looked for the signal at his home about 500 yards away there was nothing there, and I didn’t have the skill or gear to know what to do. I had a multimeter but no ‘scope. I could do the RAE, with a general electronics background and revising the licensing terms on the train up from southeast London to City and Guilds which was taken in what the University College London building in Malet Street. Imposing joint, I think it looked like this.

Somewhat doctored form of my old RAE ;) — Somewhat doctored form of my old RAE 😉

I got into Imperial. Didn’t do anything with the pass for over ten years until I came to Suffolk, and there were a few radio amateurs in the group I joined, and I got my amateur licence in 1991 – next year I will be eligible for the QCWA 😉 Initially I used a modified Tait PMR rig on 2m, but getting crystals cut got old quickly because it was dear. I then bought a secondhand FT290. However, I was living only 15m above sea level in the town, and I never got my head round all this propagation malarkey, and not having Morse meant I had to stay 6m and up ISTR. I stuck with 2m and I was never going to be doing this working the world thing without HF[ref]I’ve simplified things a lot – I had technical and engineering skills but no talent for operating[/ref], and was always a second class licensee ‘cuz only Real Men used HF.

The Internet and Amateur radio

Packet radio and the early TCP-IP over KISS modems was interesting and how I learned some of how routeing went. Then the Internet happened and basically ate amateur radio’s lunch, well, what was left of it after GSM mobile and SMS became widespread. It’s difficult for anybody born after 1990 to realise just how poor communications were, but in the end when you want to just get in touch then a modern mobile phone has solved most of the problems amateur radio had uniquely addressed, if we leave out the self training and experimentation lark. Amateur radio had been doing okay with data communications and packet AX-25, but then that Berners-Lee chap invented the Web, and broadband showed up. It looked like game over, and, well, as for so many people, life and work kinda gets in the way.

A different era, and different applications

Recently I had a use for APRS, and I take another look and I like what a new generation have done with amateur radio, they’ve grabbed it by the short and curlies and dragged it into the 21st century, working with modern networking and tech rather than harking back to the golden days of Morse and tubes. I have nothing against Morse or tubes and indeed now that I don’t have to pass Morse to get on HF I am messing about with it.

I read James M0ACQ’s blog about how he went from a standing start to Full Licence in a year. Not only is he doing good stuff with it and indeed some things I may take a fancy to, but there seem to be others doing more with it.

Continue reading “Revisiting Amateur Radio”

Growlight experiments using LEDs

We are going to do some experiments trying to lengthen the day light-wise on salad leaves, getting them jump started to harvest earlier. Britain is a funny place to grow things, the maritime microclimate means it is relatively warm for the latitude. The growing season can be limited by temperature and/or light. Because we are warmer than typical for the latitude there might be some mileage in tackling light. Britain is basically warm and dark from a plant POV. You tackle temperature using a greenhouse, or in our case a polytunnel.

the mounts let us set the lights higher as the seedlings grow

Trouble is we have no power on site, so this is an LEDs and leisure batteries job. It’s easy enough to turn off the lights once real light is bright enough[ref]I went off this after reading the Philips material and some other web research in favour of a straight time switch[/ref], but a leisure battery gets trashed if I just let it run down too much, ideally I want to pull the load once it’s down to 11.5 V or so. This gets complicated when you have something charging the battery too, but the whole point I am trying this is because we are around the Winter Solstice so there’s not much light about. So the only way that battery is going to get charged is for it to be recovered, changed out, charged and reinstalled. So once the battery gets lower than 11.5V it’s time to pull the load and keep it pulled until the battery power is reset. Even if the battery level creeps up above 11.5V off load that load should still stay off.

the batetery, timer and low-voltage cutoff — the battery, timer and low-voltage cutoff

What LED colours?

LEDs give the opportunity to favour certain wavelengths – leaves are green because plants don’t use much green, which gets reflected back for us to see.

Red and a little blue seem to be the principal colours used in this Yorkshire facility — Red and a little blue seem to be the principal colours used in this industrial Yorkshire LED4CROPS facility

Red and blue seem to be the light colours wanted, with more blue in the initial stages, red for the flowering stages. This seems to be starting to be big business, though I do somewhat wonder at the approach taken. Many of the woes of industrial agriculture stem from its arrogance in separating variables and hitting one particular aspect for all its worth – chemical farming addressing nutrients but destroying soil micro-organisms that have cycled nutrients for millennia resulting in veg that increasing lacks trace elements (the McChance and Widdowson The Composition of Foods longitudinal research) and tastes of bugger all being one example. There’s a difference between trying to push things a bit but still working with natural light and growing stuff in windowless warehouses and hubristic statements like

We are beginning to understand that growing crops in this way can improve their quality in many different ways, from their shape and colour to their flavour and nutritional value. We could, for example, increase plants’ vitamin C content.

Hmm. Maybe if we could answer why the mineral content of industrially grown foods has been falling and often tastes bland compared to 30 years ago or more I’d have more confidence in that statement. Can’t argue that yield has gone up due to industrial farming, but quality?

Back to the LEDs – we will always be short of power, though at least we are growing plants that can grow okay in the UK – salad leaves, just trying to advance them. Many people who use grow lights are trying to grow five-pointed leaf plants that aren’t typical UK horticulture. We should be having an easier job 😉 We are dealing with seedlings, which also makes life easier – we can get the LEDs much closer to the plants, a few centimetres. The RHS publication Science and the Garden: The Scientific Basis of Horticultural Practice seems to support this on page 211 which is just as well given our power limitations

Other sources on the web

LEDgrowlights seems to have to good stuff on what to look for in a grow light. Philips have got into this field, their 18W LED grow-lamps seem to be targeted at the flowering stage and it’s clear that red, deep red and blue seem to be where the action is, and NASA also seems to favour red and blue, indeed they seem to have had grief with just red in their early test.

Constructing a battery monitor/power manager

This is easy enough because I am looking for the battery voltage to drop below 11.5V after which I will shut off the lights. By putting this on our RF network I get the status reported back, and by using the Ciseco RFu I get an almost-free arduino chip so I can throw in a temperature monitor, as well as manage down the shocking 7mA quiescent current of the Arduino by sleeping it most of the time[ref]the ATMega 328 does have a watchdog timer but it’s a slight git to use with the Arduino[/ref].

Measuring the battery voltage depends on the reference voltage which is supplied by a KY5033 linear regulator (Texas LP2950 fixed 3.3V) There are actually pretty good, within 2% across -40 to 100C, which is better than the 5% tolerance of my resistor divider, which I want to arrange so the output is 3.3V/2 when I apply 10.24V, which can be done with a 115kΩ top resistor into a 22kΩ lower resistor. The total string draws 12/137 mA which is about 100uA, and the source resistance is about 18k, above the 10k recommended in the datasheet but I am only looking for about 8 bits of resolution. I could put a capacitor across the ADC input to improve that, but I can live with the error.

Jeelabs shows I could take this a lot further, but it’s good enough. I will be powering a string of LEDs drawing about half an amp for half a day or more, so as long as someone gets to the battery in about a week after it shuts down I will only have drawn another 0.02Ah from this cause, plus a bit more from the temperature and RF reporting for a few seconds every 15 minutes.

Results – failed

because we couldn’t keep the power up long enough, it just needed too many changes of batteries. We were also fighting the fact that the lighting blocks some of the daylight, so it was probably overall a reduction of light.

I have had success using three 11W CFL lamps about 60cm above some seedlings at home where power is available, so the idea of manipulating light is sound. But it’s not low-power, unfortunately, even with LEDs.