RC glow plug driver and voltmeter: constructive criticism needed - Page 1
Forum section: electronics / beginners

author: fmzambon
author_rank: Contributor
timestamp: April 21, 2018, 02:19:00 pm
content: Hello everyone,my name is Andrea Zambon, I'm from Italy and I've been curious about electronics for a long time. I've never really built anything even modestly complex until now, as I don't have any formal training in electronics (apart from a digital electronics course at the university, but nothing at all about analog stuff), I'm here to ask for some constructive criticism about my project.Also constructive criticism about my english is welcomeSo, this comes from another hobby that I have, RC model airplanes. As I like quite a bit glow plug engines, I decided to build my own on board glow plug driver. This is a circuit whose purpose is to heat up the engine glow plug(s) when the engine is at idle.For those who don't know much about glow plug engines, these engines do not use a regular spark plug, but instead have a glow plug that must keep on glowing red-hot as long as the engine is running. Starting the engine is accomplished by connecting an external voltage source (either DC or PWM) to this plug to heat it, then the engine is turned over and (sometimes) it starts. Once running, the heat inside the engine keeps the plug glowing, so the external voltage can be removed. However if the engine is capable of idling very slowly and/or if it is a 4-stroke engine (that fires only once every 2 complete revolutions of the crankshaft), then the heat from the combustion events may not be enough to keep the glow plug hot enough, and the engine can stop.From an electric point of view, a glow plug is basically a resistor (with a fairly high positive temperature coefficient as far as I can see). If one applies about 1.2V to it, it starts glowing orange and that temperature, combined with the pressure inside the engine, allows the fuel mix to ignite. In this situation a glow plug draws about 3A of current. If it is soaked in fuel and oil, the same glow plug can draw even more that 4.5A, and that's with the burden voltage of the meter in series with it.So, back to the project: I wanted to build a circuit that checks the position of the engine throttle (checking the PWM signat that the radio receiver sends to the throttle servo) and, if it is under (or over, depending on how the servo rotates) a given limit, then it must turn on glow plug heating.I already have a small circuit I built a few years ago that does this (http://www.ef-uk.net/data/rc-switch.htm), but it has some drawbacks:1) it seems to be strongly temperature-sensitive, so I often have to adjust its trigger point;2) It was built on a veroboard, so it's larger than it really needs to be;3) Partly due to the previous point, its connectors are placed in inconvenient positions.Together with this will to improve the old circuit, I also currently have a small bargraph voltmeter mounted in my plane, just to keep an eye on the receiver battery voltage. Having a single circuit doing both of these tasks would be preferable, so I'd also like to incorporate a voltmeter functionality.So I started with the voltmeter. I wanted to replicate the behavior of the voltmeter that I currently have installed in the airplane, that is the crossover point between the two lowest LEDs must be at 4.65V and the crossover point between the two top LEDs must be at 5.25V (the receiver battery is a 4-cell nimh battery). Also, if the voltage is outside of this range, then the bottom or top led of the bar should remain lit.I followed the design procedure illustrated in EEVblog #204 to use an LM3914 (changing the values according to my needs) and sure enough... it didn't workTurns out that I had missed the point in the datasheet where it is said that all inputs must be at least 1.5V below the positive supply voltage. Dave didn't have this problem with his design, but I stumbled right on it.Ok, lesson learned. I changed the input divider ratio to try and avoid that problem and sure enough it started working, but then another problem popped up: the LM3914 didn't seem to work as expected. There was a large overlap between the segments with the chip set for dot mode, much more than the 1mV value reported in the datasheet. Even when one considers the voltage coming out of the input resistor divider the overlap was still much more than 1mV.This one had me banging my head for some time. I thought I had some kind of oscillation problem, so I tried decoupling everything that could even remotely benefit from decoupling... until I noticed that the datasheet mentions that dot mode is only usable when the voltage across the whole divider is at least 500mV, and I was quite a bit below that figure.The head banging turned to head scratching about how could I increase the voltage acrosse the divider. Then it occurred to me that I could drop the input voltage by a fixed amount rather than divide it. This would keep the voltage across the divider quite a bit higher. I thought I could use a zener diode to drop the input voltage by a fixed amount, so that did sound easy.But more head banging followed. my 3.3V zeners seemed to drop much less than that. I tried with other zeners that I had bought and all of them seemed to drop significantly less than their advertised value. A look at their datasheet revealed that their zener voltage is measured at 20mA, while I was trying to run them at about 1mA...No way I'm going to piss away 20mA just for a zener, so back to the drawing board. I casually discovered the TL431 voltage reference and, after reading its datasheet, I decided to give it a try. Basically I used a TL1431A to shift the input voltage down by 2.5V, the load being provided by an LM334 set for 1mA. This then goes through an RC filter to slightly smooth it out and then goes into the LM3914.Now we are talking! Crisp segment transitions and all. But it's not yet "winner winner chicken dinner" time (did I spell that correctly?). I wanted a bargraph display that kept on the bottom or top led when the voltage was outside of the measurement range. The LM3914 already does that for the highest LED, but not for the lowest.More head scratching, a couple of PNP transistors and a few resistors produced a working solution.Satisfied with the voltmeter I went to the glow plug driver. The idea here is to generate a fixed-length pulse whenever a pulse from the receiver is detected and then check which one of the two pulses ends sooner. I didn't like the idea of using a 4013 as a monostable as in the old circuit. I wanted a proper timer chip, so it's 555 timeI decided to use a TLC555 (CMOS version, as I didn't need the high power output of the bipolar one) and configured it as a monostable. But then I had to find a way to trigger it.The 555 is low-level triggered, while I basically needed a positive-edge triggered timer for this circuit. I solved this by using a CMOS inverter (a totem pole of a VP3203 and a BS170) followed by a differentiator, whose output then goes to the 555's trigger.But then I had to find a way to sample the two square waves (the one coming from the receiver and the one coming from the 555) to see which one falls sooner. I went back to the 4013 for this, used the output of the inverter mentioned earlier for the clock of the 4013 and the output of the 555 served as the data input. This way when the receiver pulse goes back low, the output of the inverter goes high, this clocks the 4013 which samples the output of the 555.Ok, so I breadboard this, connect it to the receiver mounted in one of my airplanes and... it doesn't workOr actually, sometimes it works and sometimes it doesn't, which is probabily even worse.Turns out that I had assumed that the signal coming out of the receiver would be at the same voltage as the battery voltage, while this is not the case. It looks like this signal is capped at 3.3V, even if the battery is at over 5V. My little totem pole inverter couldn't do much...So I replaced my totem pole inverter with a single BS170 inverter/level shifter to bring the signal up to 5V and that seemed to fix the problem. I had to use separate inverters for the 555 trigger and for the 4013 clock because the differentiator slows down the rise time of the inverter output, but that's not a big deal.I only tested this part of the circuit up to the 4013 outputs, as after that there's not much going on. The IRF3711 is the same MOSFET type that I'm currently using with my veroboard-built circuit, and it seems to work fine. The circuit only provides an open-drain output to control the power being sent to the glow plug(s). The power itself is provided by an external D-size nimh cell.In the end I attach the schematics I came up with (vm is the voltmeter and gd is the glow plug driver). Some elements are missing a value:D1 is a 1N5819 Schottky diodeQ2 and Q3 are MPS2907All caps are ceramic, except for polarized caps (that are aluminium electrolytics) and for C8, which is a Polypropylene cap (for temperature stability)All resistors are metal film resistors (1% tolerance)The potentiometer is a single turn trimmerThe "on off on switch" next to the 4013 chip is mounted externally to the circuit, connected by wires. It basically connects either the Q or -Q output of the 4013 to the following part of the circuit. The center position disables the circuit.And here is the question: can anyone see anything that could use some improving?

author: Cerebus
author_rank: Super Contributor
timestamp: April 21, 2018, 10:44:39 pm
content: Andrea, welcome.That's a bit of a mammoth post for a first one. Normally by now someone would have commented - I suspect people have been put off by the shear mass of text staring at them from the screen. Full points for thoroughness, some could learn from that, but so much to digest followed by such an open ended question is probably a bit too big an ask. Perhaps you'd get more traction if you suggest concrete areas you want to see some improvements for - what features do you think are sub-optimal?

author: fmzambon
author_rank: Contributor
timestamp: April 22, 2018, 12:52:27 am
content: Hi Cerebus,yeah, I kind of expected people to be put off by the text wall...I spent some time to come up with those schematics so I could either post them in here without any explanation and just ask for an opinion (likely followed by a stream of posts where I'd have to explain most of the choices I made) or try and explain why I did what I did up front (even though I knew it would turn out to be a long post). I chose option 2, so here's the text wallAnyway, as for the question, I'm basically asking whether I made some rookie mistake that I'm missing. Or if someone finds a way to achieve the same result in a simpler way.For example, is my solution to keeping the bottom LED of the bargraph lit valid? Or is there a simpler way?I know that the base of Q2 must pass the current needed to light up one or two leds of the bar, so we're talking about 40mA max through the base of that transistor (that's with two LEDs lit; with one LED it is 20mA). I couldn't find an explicit spec for the maximum base current of the MPS2907, even though some graphs imply a base current of up to 50mA. Any opinion about this? Is it safe to run 40mA continuous through the base of an MPS2907?Is my use of a TL431 and LM334 something that is commonly done? Does it have any drawbacks that I'm missing?The differentiator before the 555 timer seems somewhat complex, but I didn't want the trigger voltage to spike above the positive rail, hence the diode and the additional resistor R11. Is this solution reasonable?Any opinion about using the 555 output to feed the RC timing network rather than using the positive supply rail?Is R16 needed at all? Or can I just connect the output of the 4013 straight to the gates of Q1 and Q6 without any gate resistor? I ask this because this circuit should only switch those MOSFETS once in a while, so maybe one can omit the gate resistor.Here we go again, another mini text wall

author: Cerebus
author_rank: Super Contributor
timestamp: April 22, 2018, 01:41:54 am
content: Erm, I'll get back to you - maybe. Not really quite my kind of thing, I just really wanted to give you a heads up as to why you might be led into thinking people were ignoring you. Bedtime now, I'll try and remember to come back and review this properly once I've got a couple of cups of coffee inside me tomorrow - I might even have something actually useful to say.

author: james_s
author_rank: Super Contributor
timestamp: April 22, 2018, 03:35:29 am
content: If you have any interest in software development, a microcontroller is a very easy way to do this. There is an Arduino library that will turn a servo signal into a number at which point you can easily toggle the state of a digital output at any throttle setting you want. The attiny arduino clones are small and cheap.

author: Ian.M
author_rank: Super Contributor
timestamp: April 22, 2018, 05:36:35 am
content: Yes. The MCU's ADC can handle the battery voltage monitoring, via a simple potential divider, so that gets it down to one MCU + a LDO regulator, a couple of capacitors, a few resistors, the LEDs and the MOSFET. Done in double sided surface mount, SMD LEDs on one side and an ATmega328 in its 4x4mm QFN package + the other components on the other, it could possibly be as small as a large postage stamp while retaining full Arduino Mini software compatibility.

author: fmzambon
author_rank: Contributor
timestamp: April 22, 2018, 08:17:54 am
content: Hi all,I was kind of expecting the MCU reply. In fact I work for a (small) firm building e-commerce websites, so I don't think that controlling some LEDs with an MCU would be a problem.But, for this very reason, I'd rather do it the old fashioned way and use analog or hardwired digital electronics for a bit of a change.Also I'm not very good at soldering, so I'd rather stay with through-hole components. I know that surface mount is smaller and lighter, but this circuit is going into an airplane that is 2050mm in wingspan and 4kg in weight, powered by a 15cc 4-stroke boxer twin engine, so saving 10 grams won't make much of a difference....and yes, I did write my last reply at 3AM local time

author: james_s
author_rank: Super Contributor
timestamp: April 22, 2018, 04:20:24 pm
content: Well there's nothing wrong with the old analog approach, I only suggested the microcontroller as an option.Perhaps an even easier method is to mount a microswitch to the throttle servo and grind a cam into a round servo horn. With some care you could have the switch close when the throttle is in the idle range. No electronics fun but it doesn't get much simpler.

author: fmzambon
author_rank: Contributor
timestamp: April 23, 2018, 07:13:42 am
content: Quote from: james_s on April 22, 2018, 04:20:24 pmGood point, a microswitch could most likely do it.There's a few points to consider though:1) I'm not sure I could use the same servo I currently use for the throttle to operate this cam as well, as I fear that the current servo arm would interfere with the cam. That would possibly require a creative installation of the switch or perhaps a separate servo;2) adjusting the operating point would involve physically moving the microswitch or rotating the servo cam, both of them less conveniente that adjusting a trimmer;3) last but not least, running the full glow plug current through the microswitch may not be a good idea. We're talking relatively high current (around 3A per plug) at a very low voltage (1.2V). Any excess wire or contact resistance is going to drastically reduce the amount of power delivered to the plug, resulting in harder engine starting. However it would be possible to use the microswitch to turn on the mosfet, thus removing the 555 and the 4013.In the end I think that the all-electronic approach is superior to a microswitch: smaller, lighter (non that it matters all that much as I said, but...), easier to install and adjust. So I'm staying with that for now, unless some other idea comes around

author: max_torque
author_rank: Super Contributor
timestamp: April 23, 2018, 12:04:18 pm
content: I'd suggest using the resistance of the plug itself to determine if it should be on!The wire of the glow plug acts as a point ignition source, either by being internally heated by the electrical current flowing through it (cold starts and light loads) or by being heated by radiation from the burning cylinder charge. At some load and speed, enough radiation energy is absorbed by the wire to keep it hot, meaning you don't need to drive any additional current through it.This way you don't need any additional sensors or mapping for the system!Obviously, you can't let the plug get too cold, so your system would have to drive the plug for a bit, then quickly check it's resistance, and then decide if to drive it for a bit longer etc

author: Rerouter
author_rank: Super Contributor
timestamp: April 23, 2018, 12:24:54 pm
content: My thoughs for dumb analog would be1x Op amp - Howland current source (He provides the measurement current1x Op amp - Oscialltor (He switches between measure and heat)2x Op amp - Sample and hold (He holds the measurement result, and gets reset by the oscialltor)1x op amp - Comparitor (If your below your desired voltage, turn on the heater for the heating cycle)So how you arrange it is up to you, but for the howland current source, its very easy to make them for above ground, you can probably leave him running if the current is small, the plug heat will be based on its resistance,So now the meat of it, the oscialltor disables the comparitor (probably via summing with one of its inputs) for the measuring phase, and updates the sample and hold,Then for the heating phase the sample is fed to the comparitorThis would be a loose PWM, mainly because based on thermal mass, I'm going to guess the response time is multiple seconds, not fractions of a second,Equally there is no reason the duty cycle has to be 50/50,I will say this way is fairly idiot proof, if the wiring fails open, it thinks its over temp and never heats, and if its shorted, well its not heating the plug.

author: oldway
author_rank: Super Contributor
timestamp: April 23, 2018, 01:33:24 pm
content: As far as I remember, a french member of this forum have developped a project on this forum to solve the same problem.You should use the search fonction to find it.

author: fmzambon
author_rank: Contributor
timestamp: April 23, 2018, 01:57:30 pm
content: Quote from: cleaningOut on April 23, 2018, 08:15:27 amWhere's the fun thenIn addition, you can't beat the sound of a multicylinder four stroke engine

author: fmzambon
author_rank: Contributor
timestamp: April 23, 2018, 02:06:50 pm
content: Thank you max_torque and Rerouter, these are very good ideas.I had thought about sensing the plug resistance, but dismissed it as too complex without an MCU (as I said I'd rather do it "the old way"). I'll definitely investigate the options suggested to add temperature sensing. I'd probably have to incorporate some kind of adjustment anyway because different makes and types of glow plugs seem to have drastically different resistance values, so I can't just hardwire a current value and call it a day.oldway, as for the project of the french member, is it this onehttps://www.eevblog.com/forum/projects/improving-glow-plug-drive-design-for-rc-plane-radial-engine/?I guess it's a modeller's trait to start with a text-wall first post

author: oldway
author_rank: Super Contributor
timestamp: April 23, 2018, 02:26:21 pm
content: Yes, it is....What do you think about it ?

author: fmzambon
author_rank: Contributor
timestamp: April 23, 2018, 02:34:24 pm
content: Quote from: oldway on April 23, 2018, 02:26:21 pmAbout the project or about the text-wall first post?Joking aside, I need to check that project more carefully. I'm at work now (waiting for an automated test procedure to end), so I don't have that much time at the moment.

author: fmzambon
author_rank: Contributor
timestamp: April 23, 2018, 07:37:41 pm
content: @oldway: So, I read through that thread I linked a few posts back.It seems like that project is trying to do MUCH more than I'm trying to do here. Hall effect sensors to detect glow plug current, cylinder temperature sensors and, in the end, barometer, airspeed sensor, Bluetooth connection...Basically a miniature ECU, it's only missing fuel mixture control.Quote from: Rerouter on April 23, 2018, 12:24:54 pmI was thinking some more about this suggestion. It may not be ideal to incorporate it in the current project, as the driver that I'd like to build is powered by a NiMH cell, so no PWM would be used here. In fact PWM would interrupt power to the plug, thus reducing the RMS voltage applied to the plug itself, which is already marginal.However in a few months I'll build a glow plug driver for a 5-cylinder radial engine and I was planning to use a lithium battery for that (LiFe battery most likely). Hence I'll need to PWM the plugs and then your idea would mesh in nicely.If I may, for the first 2 points I think that one may not need "explicit" op amps: I already experimented with the LM334 current source, so maybe I could use that instead of a Howland current source as you proposed (but I didn't know that current source type, so that's nice to know). And the oscillator could very well be a 555 or any other oscillator chip.In fact I could configure the final op amp as a differential amplifier rather than as a comparator and feed the output of that into the control voltage input of the 555. I need to think more about this, but it could work.As an aside, I have a clear feeling that I have read kikinou's (the outhor of the other, linked thread) original attempts at powering a glow plug with a PWM waveform using a 555 timer, but I can't find that thread anymore. I clearly remember that someone was burning plugs and that was because he assumed that for a PWM signal Vrms = D*Vin (D is the PWM duty cycle), whereas the correct formula is Vrms = sqrt(D)*Vin. Hence he was using too high a duty cycle and burning out plugs.I already built a PWM glow plug driver based on a bipolar 555 astable and a bank of mosfets for my engine test stand, and I can confirm that it works just fine. If one uses the correct duty cycle, that is. And if one solders the 555's bypass capacitors correctly... (why is it running at 30+ kHz rather than the designed 350Hz?)

author: oldway
author_rank: Super Contributor
timestamp: April 23, 2018, 08:00:56 pm
content: I can not comment on either your project or that of Kikinou because my experience in model aircraft dating from my youth and we made the circular flight with the engine still at full throttle ...Apart from the webra boxer 2 cylinders, I do not remember multi-cylinders engines at the time.My favorite engine was the 2.5cc Cox Olympic, a very powerful engine that ran at 20,000 rpm.I have to make a suggestion: change the title of your topic so that we know what it is about.

author: fmzambon
author_rank: Contributor
timestamp: April 23, 2018, 09:51:12 pm
content: Quote from: oldway on April 23, 2018, 08:00:56 pmDone

author: james_s
author_rank: Super Contributor
timestamp: April 23, 2018, 11:54:44 pm
content: A friend of mine has a nitro radial engine for a model airplane, it's an impressive piece of craftsmanship but he's never flown it in a plane, it's too valuable. He had a good point that with a multi-cylinder glow engine it's possible for one or more cylinders to die without it being obvious to the pilot on the ground, until you need to suddenly open the throttle and realize not all the power is available. I suppose that's what this proposed circuit is to prevent.

author: Rerouter
author_rank: Super Contributor
timestamp: April 24, 2018, 10:06:05 am
content: Sat down and drew up my op amp based approach, Its still there if the op wanted something analoghttp://tinyurl.com/ybuqrljtFull link below if it expires.Code:http://www.falstad.com/circuit/circuitjs.html?cct=$+1+0.000005+10.20027730826997+58+5+50%0Aa+-176+144+-64+144+0+5+0+1000000+0.04950889799120179+4.036530011794033%0Aw+-64+144+-64+80+0%0Ar+-176+208+-64+208+0+100000%0Ar+-176+80+-64+80+0+100000%0Ar+-176+80+-288+80+0+1000%0Ar+-288+208+-176+208+0+1000%0Aw+-176+160+-176+208+0%0Aw+-176+80+-176+128+0%0Aw+-176+208+-176+256+0%0Ax+702+293+790+296+4+24+Setpoint%0Ag+-288+80+-320+80+0%0AR+-288+208+-320+208+0+0+40+5+0+0+0.5%0Aw+-64+208+-64+144+0%0A181+32+256+32+336+0+1065.4064433491974+25+5+1+1%0Ag+32+336+32+352+0%0Aw+-176+256+32+256+0%0Af+96+176+32+176+1+1.5+2%0Aw+32+192+32+256+0%0AR+32+160+32+128+0+0+40+5+0+0+0.5%0Ac+288+80+288+144+0+0.00001+0.34995086109383294%0Ag+288+144+288+160+0%0Ar+288+304+192+304+0+10000%0Ar+368+304+288+304+0+10000%0Ar+192+208+288+208+0+10000%0Ar+368+272+288+272+0+1000%0Ac+368+208+288+208+0+0.000001+-3.4175819977216473%0Ag+368+208+368+224+0%0Aw+288+272+288+304+0%0Aw+192+256+192+208+0%0Aw+192+256+192+304+0%0Aw+288+208+288+240+0%0Aa+288+256+192+256+0+5+0+1000000+3.4175819977216473+3.236797676118947%0Aw+288+80+560+80+0%0Aw+560+80+560+256+0%0Aw+96+176+192+176+0%0Ag+368+304+400+304+0%0Aa+560+272+464+272+1+5+0+1000000+0.34991378270596496+0.34995086109383294%0Ac+464+336+560+336+0+1.0000000000000001e-7+3.357925004091883%0Aw+464+336+464+272+0%0Aw+560+336+560+288+0%0Ar+624+288+560+288+0+100%0AR+624+288+672+288+0+0+40+0.35000000000000003+0+0+0.5%0Aw+192+176+192+208+0%0Aw+464+272+368+272+0%0Ar+368+336+288+336+0+10000%0AR+368+336+400+336+0+0+40+5+0+0+0.5%0Af+192+176+192+80+8+1.5+0.02%0Aw+-64+80+176+80+0%0Ax+243+362+431+365+4+24+Minimum%5CsOn%5Cstime%0Aw+288+336+288+304+0%0Ar+208+80+288+80+0+10%0As+32+256+96+256+0+1+true%0AR+96+256+128+256+0+0+40+5+0+0+0.5%0Ao+8+64+0+4099+10+0.0125+0+2+8+3%0Ao+28+64+0+4099+20+0.0015625+1+2+28+3%0Ao+13+64+1+20491+5+12.8+2+1+40%0A

author: fmzambon
author_rank: Contributor
timestamp: April 25, 2018, 05:24:59 pm
content: Thank you very much Rerouter, that circuit will be very useful

author: fmzambon
author_rank: Contributor
timestamp: December 16, 2019, 09:42:33 pm
content: Hello everyone,I'm resurrecting this old thread (has it really been one and a half years???) for the benefit of anyone who might find it while looking for a similar circuit.I ended up building the circuit of the first post. It worked as intended, except for a minor goof-up.R5 and C1 are intended to form a low-pass filter to smooth out any high frequency noise on the supply voltage. I had thought "470R, 100nF, yeah, an RC filter with a 47ms time constant should be enough to filter out high frequency noise and still have a reasonably fast response for the voltmeter". Except that 470R and 100nF give a time constant of 47us, not 47msOh well, what's three orders of magnitude?I didn't spot the mistake right away because the older analogue RC receiver that I used for the tests seemed to have a farly constant current requirement, so the low pass filter wasn't really called into action. But the newer digital receivers seem to have a pulsed power consumption.The first attachment is the situation with the original component values. The upper trace is the signal before the filter, the lower trace is after. 1X probes, so that's a 70mV voltage dip. The power comes from a 4 cell NiMH battery, so nominal 4.8VChanged R5 from 470R to 47k and C1 from 100n to 1u (didn't want to go to 470k because I feared that that could be too much impedence for the LM3914). The second image is the result.When i wiggle the controls to cause some "real" current spikes from the servo motors, the meter still seems quite responsive. So I'd say it's a good compromise.The last picture is the actual circuit installed in the airplane. Yes, I did fly it, and it did work as intended both on and off the groundSome improvements should I ever get back to this (or should anyone consider replicating this circuit):* I included the 5mm round green LED as a power indication, but it is fairly redundant given that one led of the bar is always on. So that could be omitted and replaced with a simple resistor;* Perhaps one could add a capacitor across the TL1431 voltage reference, as I found that some noise gets through. Obviously it's necessary to read the datasheet to know what values of capacitors will not cause oscillation issues and do some experiments.And finally, I haven't forgotten the suggestions for more advanced control schemes, such as sensing the glow plug voltage and using that to adjust the amount of power supplied. I fully intend to do that, but it's going to be another projectEdit: goofed up the attachments

author: james_s
author_rank: Super Contributor
timestamp: December 17, 2019, 06:57:44 pm
content: Good to see a followup, a lot of threads like this end with no update on the outcome. Looks like a tidy layout, do be careful with those screw terminals though, they have a tendency to work loose. The vibration of a small glow engine also tends to be very good at loosening fasteners.

author: fmzambon
author_rank: Contributor
timestamp: December 18, 2019, 08:20:36 pm
content: Quote from: james_s on December 17, 2019, 06:57:44 pmI've already used screw terminals in this very same model, and never had an issue. Perhaps it's because its engine is a twin cylinder boxer engine, which does not vibrate all that much?Still, I'll keep an eye on them