 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Microcontroller and PC projects : Flash 3 common catode LED lamps.
  Page 12 of 12 |
|||||
| Author | Message | ||||
Mixtel90 Guru  Joined: 05/10/2019 Location: United KingdomPosts: 5705 |
Correct. I've used a 15v zener gate-source in the past. I don't like to get too close to the maximum rating. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
||||
CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 1985 |
ARGH! Yes of course. school boy error  I was prefixed on the source of a lo-side. dammit Edited 2021-08-18 20:05 by CaptainBoing |
||||
| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5705 |
Please check Bob's post,folks... If he's happy to use those (not necessarily in self flashing mode) then there's no need to consider high side drivers now. He can use his bucket of N-channel mosfets. No protection or anything needed, just a 100R anti-parasitic resistor connected right on the gate lead. A 100k turn-off resistor would be nice as the arduino probably powers up with it's pins high impedance until the program sets them up. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
||||
| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
I don't think that I have ever come across low-side switching for external circuitry.  |
||||
| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5705 |
I was once told that it's not normally done because accidentally grounding a load lead energises it. I don't know if that's true or whether it's just convention. It's quite likely that it's not done on voltages above 50v because of shock risk. I think it's better to pick whatever system works in a particular case really. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
||||
phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 1773 |
Re low-side switching, used to be common in many cars. Toyota and Nissan used it for the headlights, wipers, horn & interior light. Bob may use the new lights, but may also use the old ones. As long as he does not want them to stay on continuously for more than a few seconds a bigger capacitor (10uF to 100uF?) may do the job. Along with the G-S Zenner and a resistor across the LED to ensure the capacitor charges fully despite the nonlinearity of the LEDs - it's charge path is through the load. Looking back, this has all been covered several tines before. |
||||
| CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 1985 |
definitely. Everything had a switch to the chassis for the ground return. I still check which way round it is when i work on car electrics. |
||||
| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 639 |
You have done it now CB. My 1949 Morris Minor did not have low side switching. In fact it had very little switching of any sort (it was LUCAS after all). I have been using the ULN2003 anything driver for many years with no problems. It is one of those "how did we live without it" things. When I was checking up on the ULN2003 I came across a new chip designed to drive LEDs. It can do every thing but sadly I forget what it is called. Nothing like a good argument.  Peter |
||||
| CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 1985 |
really? even the brake switch? -Mounted above the pedal if it has a single wire it can only switch to chassis "earth" (lo-side). UNLESS... horror of horrors, it was "positive earth" (atch, nothing wrong with it, just goes against the very fibre of my being  )same with oil pressure sensor -a stud in the engine block with a single wire - oh, wait... you said 1949... was oil pressure sensing even thought of then? Well... I say "sensing" I always thought those pressure switches lead to a "engine destroyed" light on the dashboard coz if it got low enough to switch it was too late  .1949, that moggy must be one with the headlights in the grill and a split windscreen? Edited 2021-08-19 20:45 by CaptainBoing |
||||
| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5705 |
"designed to drive LEDs" usually means constant current outputs up to a max of about 50mA. I doubt if they would work here. Lovely idea though. :) Incidentally... has anyone realised that you can connect a resistor to TP5 on the PicoMite to the base on an NPN transistor and use it as an output? The only problem is that TP5 only goes up to about 2v while the LED is on, otherwise it's a conventional digital output. You may even be able to define it as an input and power the LED from an external supply, but I haven't attempted that. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
||||
| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 639 |
The brake switch was operated by hydraulic pressure, there was probably a more difficult method but nobody could think of it. You are correct, it must have been low side. Oil pressure was displayed on the dash via a copper pipe. It was more of a temperature indicator because the MM didn't have a temp gauge. If the oil pressure got a bit low it was overheating. The battery was pos. ground. Fortunately good radios could be both. The MM did not come with a high beam indicator, you had to fit your own. And it didn't come with an interior light. But Nancye still talks about it with great affection. She didn't have to do those 50 mile late night drives with no heater. I'll have to find those LED drivers. As promised STCS1 1.5A, 40V. Peter Edited 2021-08-19 21:13 by PeterB |
||||
| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5705 |
Nice little chip, Peter. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
||||
| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 3493 |
STCS1 = low side switching PicomiteVGA PETSCII ROBOTS |
||||
| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
|
||||
| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 639 |
Volhout. Mick and Tinine were having a discussion about low side switching. They seemed to think that it is never done which bothered me because I thought that I had been doing it for years. So I thought perhaps it was all in my head, quite possible at my age, however I found the ULN2003..............well I think I did. Peter  |
||||
| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5705 |
I was thinking in industrial control gear terms. You don't often find low side switching there - although it is done. I've done it myself in control panels when, for example, the common of a changeover contact is grounded for some reason. General control electronics is something else, especially if you want high currents as PNP and P-channel are both more expensive than using NPN and N-channel. ULN2003 has been a mainstay in this area for a long time. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
||||
| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
Yeah, when I think of the self-titled "electrical engineers" (maintenance sparky) that I come across, they are looking for the presence of a 24v signal, not the absence of a 0v. They'd be ripping out perfectly good parts, thinking they are bad |
||||
| Page 12 of 12 |
|||||
 Print this page |
