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Forum Index : Microcontroller and PC projects : (MM)microcontroller comms problem
| Author | Message | ||||
| jeffj Regular Member  Joined: 04/02/2012 Location: AustraliaPosts: 84 |
I have just had an interesting comms problem . I was trying to download to a B/W MM using Notepad and Teraterm. It kept on losing the odd parts of the text, I tried all sorts of things such as speed delays etc . Different computers ,Teraterm and cables and Resoldered the connections. I read your posts on "maximite USB problems back from 2014" and from that decided to check the voltages. It turned out to be the volts at the 5 volt reg were down (using an external supply) I fixed that with another power supply. All good ,Comms back to normal except that now the MM shuts down after a few minuites. The 5 volt reg is running very hot I can't keep finger on it .I put a temporary heat sink on it and now ok. |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9593 |
External supply for a MM should be about 9v I would think. I seem to remember that was the voltage I used with the B/W MM when I had my first MM. What voltage are you using? Higher then 9v, and the regulator will get very hot as you have found out. It is never a good thing if a regulator shuts off due to overheating. This is a last-gasp by the regulator to safe itself, and in an ideal world, the thermal shutdown should never happen in normal operation, as it is generally stressful to the regulator. If you are feeding the MM with a 12v supply, then the regulator is having to drop 7v, and that can quickly and easily add up to quite a bit of heat dissipation depending on the current on the 5v output.  Smoke makes things work. When the smoke gets out, it stops! |
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| Bizzie Senior Member  Joined: 06/07/2014 Location: AustraliaPosts: 192 |
Grogster - What is the best way to derive a 5v supply from car or in my case tractor battery to minimize the heat buildup? Rob White |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9593 |
12v or 24v tractor? In either case, a pre-regulator is how I normally do it, depending on the output load. If it was a 5v output, and needed to do an amp or so from a 12v supply, I would use 780x series TO220 regulators, and have a 9v regulator feeding into the 5v one - the 9v one is the pre-regulator, and drops the voltage to the 5v regulator down to 9v first. In this way, BOTH regulators share the current load, and each dissipate some of the heat, but not all of it. For 24v to 5v, your best bet would be one of those cheap buck-converter regulator modules on eBay for a few dollars. EDIT: I should mention that this is thinking mainly from an on-board regulator type of concept, but if you are happy for external regulator modules, you can't go far past the likes of this buck converter module on eBay for a whole dollar fifty.... I use this very same module in my stereo project, to drop the 36v input down to 12v for the system board - which has it's own on-board 5v and 3v3 regulation. I would be inclined to simply grab a few of those eBay modules, and adjust it for 5v, as they would be fine with a 12v or 24v input, and they are very efficient so don't dissipate anywhere near as much heat as the linear 780x series regulators. Smoke makes things work. When the smoke gets out, it stops! |
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CircuitGizmos Guru  Joined: 08/09/2011 Location: United StatesPosts: 1427 |
Something like this: http://www.ebay.com/itm/6-24V-12V-24V-to-5V-3A-CAR-USB-Charger-Module-DC-Buck-step-down-Converter-DIY-/221980647793?hash =item33af13e171:g:gg8AAOSw3KFWgoDf Or this: http://www.ebay.com/itm/12V-to-5V-3A-15W-USB-DC-DC-Buck-Charger-Converter-Step-Down-Module-Power-Supply-/400981171330?ha sh=item5d5c571c82:g:YpsAAOSwLVZV1Sm3 Micromites and Maximites! - Beginning Maximite |
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BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935 |
Something like this may generate a bit less heat and allow you to do a one stage step down. The output is adjustable so you need a multimeter to set the output. There are many similar on eBay so get what suits you best. http://www.ebay.com.au/itm/LM2596-Step-Down-Module-DC-DC-Buck-Converter-Power-Supply-Output-1-23V-30V-New-/251066005460 edit This one is slightly lower powered and has a voltmeter built in. http://www.ebay.com.au/itm/Led-Voltmeter-Buck-Step-Down-Converter-Module-LM2596-DC-DC-Voltage-Regulator/350849935498 |
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| Bizzie Senior Member Joined: 06/07/2014 Location: AustraliaPosts: 192 |
Thanks Guys, It never ceases to amaze me how easy and quick it is to get info on TBS. Thanks ALL! Rob White |
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| jeffj Regular Member Joined: 04/02/2012 Location: AustraliaPosts: 84 |
Thanks for that .Yes I had a 12 volt supply . I suspected it was shutting down due to excess temperature Jeff |
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| jeffj Regular Member Joined: 04/02/2012 Location: AustraliaPosts: 84 |
I thought I fixed the problem . I lowered the power supply volts and put a heatsink on the 5v reg All seemed ok I boxed it all up and put it to work in my shed only to find that it wasn't working next day. I did a current test and the MM was drawing 850 mA.I had a spare chip so installed that and all ok .I don't really know what caused this problem but I suspect it was because I thought that the colour and Mono MMs were interchangeable as far as field conns are concerned.I have just noticed that this is not the case .The 5v and 3.3 v pins are at opposite ends .of the plug. I was using the colour one in the house to develop the program whilst I had the B/W one in the shed. I was sure I had seen a comment about them being interchangeable but cannot find it Jeff |
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