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Forum Index : Microcontroller and PC projects : Spike Suppression
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palcal Guru  Joined: 12/10/2011 Location: AustraliaPosts: 1993 |
I am running a MX170 backpack in my car from a USB outlet plugged into the cigar lighter. It didn't work for long before the MX170 failed, I suspect due to voltage spikes. What is recommended for spike suppression in a vehicle, would a zener across the supply work. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
(I trust that you're using a 12v to 5v adapter first - the display won't take 12v even if the 3.3v regulator will). Cars can be very noisy electrically. You really need a good filter. If you have a small toroid core (say, 12mm dia) wind some turns through it with 2 wires. The 2 starts go to the input supply, the 2 finish wires go to the backpack (get the polarity right!). Then put a 0.1uF and a 100uF electrolytic in parallel across the 5V to the backpack. Keep all signal wires to the backpack as short as poss. A 5V1 zener wouldn't go amiss either. Don't connect either side of the filtered supply (GND on the backpack) to anything that might be connected to the car metalwork as you'll unbalance the filter and it'll be useless. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2640 |
" Don't connect either side of the filtered supply (GND on the backpack) to anything that might be connected to the car metalwork as you'll unbalance the filter and it'll be useless." This bit can't be overstated. Any input / output devices must get power and ground only from the backpack's filtered supply. |
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| palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1993 |
Got some toroids somewhere I will knock one up. Thanks "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 655 |
G'Day PC etc. I have been using Arduino, MX170 & E64 in agricultural machines for some years and with no failures that I know of. I use a diode to protect against polarity reversal, an electro, a SMPS, a second electro and that's it. However, agricultural things use diesel engines so there is no nasty ignition rubbish but there is quite a lot of electro-mechanical stuff going on. Good luck  Peter |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5089 |
It is possible cheap car lighter USB chargers plugs have bad protection. But generally they can provide enough power. IF you overburden them they may output to high voltage, effectively killing a 3.3V regulator on a MX170 board. What is more likely, is that the car is charged (or the human entering the car) and by touching the MX170 you discharge (ESD) into it. Most project I have seen here (including Geoff's) have not ESD protection except the protection build in the chips. Especially LCD driver chips are very sensitive. PicomiteVGA PETSCII ROBOTS |
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twofingers Guru Joined: 02/06/2014 Location: GermanyPosts: 1593 |
Hi Paul, maybe disco4now's Dual Battery Monitor can provide you with some inspiration. Please see the schematics (PDF). Best regards Michael causality ≠ correlation ≠ coincidence |
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| palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1993 |
Thanks for that. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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