Source for cheap panel voltmeters? - Page 1
Forum section: electronics / testgear

author: microbug
author_rank: Frequent Contributor
timestamp: September 01, 2013, 02:38:53 pm
content: I'm making theSilicon Chip dual tracking power supply(click on one of the photos and press the next / previous buttons to get the schematic). It calls for a panel voltmeter with a 200mv full scale range and with an adjustable decimal point. Unfortunately, the cheapest 3 1/2 digit voltmeter I could find for this was around £30 ($46.50). Does anyone have a preferred source for less expensive ones - I have some cheap 3 digit ones already but they neither of the features needed.Thanks- microbug

author: pmcouto
author_rank: Unknown
timestamp: September 01, 2013, 03:11:19 pm
content: Hi Microbug,Check this one:http://www.ebay.co.uk/itm/Panel-Volt-Meter-PM-128-EBL-3-5-Digit-LCD-Enhanced-Version-Back-Light-/221233607035?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item33828cf17bRegards,Pedro Couto

author: echen1024
author_rank: Super Contributor
timestamp: September 01, 2013, 03:16:41 pm
content: I am quite interested in this circuit as well, so can you post the diagram for it? Thanks.

author: microbug
author_rank: Frequent Contributor
timestamp: September 01, 2013, 03:18:57 pm
content: It's a good start, but what I really meant was that you input 200mv and can change the decimal point from 2.000 to 20.00/200.0 . The schematic for this circuit ishere, but you may need access to the article to understand all of it - the trimpots can be confusing.EDIT: I foundthis pagewhich seems to have what I need. I will have to look into shipping though - some sellers only ship through expensive first class (which tends to cost 3x the item value).

author: mariush
author_rank: Super Contributor
timestamp: September 01, 2013, 03:23:37 pm
content: You can build some yourself using chips like ICL7106 or ICL7107 (7106 has lcd segment driver, 7107 has led 7segment digit driver )The 7107 is used for example in the Tenma psu i bought, see pictures here:https://www.eevblog.com/forum/testgear/tenma-72-8695-2-x-32v-3a-5v-2a-mini-review-teardown/?topicseenAnd you can see a 7106 used in the datasheet below, to get an idea about the extra components needed (they're not many) :An ICL7107CPLZ is about 4 pounds in 1 qty, about 2 pounds each if you buy 100:http://uk.farnell.com/intersil/icl7107cplz/3-5-digit-adc-cmos-7107-dip40/dp/9663568?ref=lookaheadRead the datasheet.If you want cheaper, then like pmcouto says, those cheap ebay multimeters simply use a microcontroller with an adc converter and a voltage divider that lowers the input voltage to 0-5v that the adc can convert to the 10bit internal values (0 to 1023)

author: Monkeh
author_rank: Super Contributor
timestamp: September 01, 2013, 03:32:52 pm
content: iloveelectronics (Franky) on this forum should be able to source you one of these:Be aware it does require an isolated supply, but this is easily enough catered for.

author: pmcouto
author_rank: Unknown
timestamp: September 01, 2013, 03:33:48 pm
content: Hi Microbug,The PM-128E will do exactly what you need.

author: microbug
author_rank: Frequent Contributor
timestamp: September 01, 2013, 03:38:53 pm
content: Thanks pmcouto, I didn't realise the decimal point was adjustable! The ebay one will probably be fine, although I will look into this meter from Franky.

author: quarros
author_rank: Regular Contributor
timestamp: September 07, 2013, 08:33:55 am
content: If you don't mind having an LCD instead of a Segmented Display than I would advise you to look up this:http://pa-elektronika.hu/hu/kesz-projektek/100-pices-panelmero-ii.htmlYou can buy this Assembled or just the parts from the designer. The page is in Hungarian but if you run it trough Google translate and it gives acceptable results. And you don't need special language skills for a schematic. It can measure the output voltage and current, and calculate the external resistance or Wattage.Side note: When you try to view the schematic or assembly pictures, don't do it from Google translate because it wont show up that way

author: eevblogfan
author_rank: Frequent Contributor
timestamp: September 07, 2013, 09:25:28 am
content: HeyI don't know what is your exact needs are , but have A look at that meter :http://www.ebay.com/itm/DC-4-1-2-Ultra-High-Accuracy-3-5-30-000V-Mini-LED-Digital-Panel-Meter-5-Digits-/170994850740?pt=LH_DefaultDomain_0&hash=item27d0165bb4I linked him because It seem to be that he can supply 10~50 of quantity if not more ,I have great experience with that meter , it has 0.01% linear response ( 10.0000V applied , it reads 10.001V , 20.0000V applied , it reads 20.002 and so on .. )basically over kill for any DIY supply , the seller also sell 3A meter , link :http://www.ebay.com/itm/DC-4-1-2-Ultra-High-Accuracy-0-3A-Mini-LED-Amp-Meter-5-Digits-Built-in-Shunt-R01-/171015790673?pt=LH_DefaultDomain_0&hash=item27d155e051If 200mV scale is needed , you might want to consider buying the 3A meter and remove the shunt and modify it to show you the voltage you apply instead ( I am guessing it has 33mV full scale due to the small shunt , I think I saw there "R01" mentioned hence 10mOhm shunt , perhaps ? ) so with 10:1 Divider you can sense 330mV full scalehe ships World wild "free" shipping

author: mianchen
author_rank: Regular Contributor
timestamp: September 07, 2013, 10:13:30 am
content: I've built one of these about a year ago with EPE mag's over priced PCBs and left it on my bench since.Quote from: echen1024 on September 01, 2013, 03:16:41 pmHere's the link to the schematic:http://archive.siliconchip.com.au/cms/gallery/article.html?a=112014&i=9

author: Tita
author_rank: Contributor
timestamp: September 07, 2013, 10:16:44 am
content: You could make a homemade one! O0With ICL7107:)http://pdf1.alldatasheet.com/datasheet-pdf/view/72696/MAXIM/ICL7106-ICL7107.html

author: mianchen
author_rank: Regular Contributor
timestamp: September 07, 2013, 10:17:12 am
content: Quote from: microbug on September 01, 2013, 02:38:53 pmhttp://www.ebay.co.uk/itm/3-1-2-Red-LED-Digital-Volt-Panel-Meter-DC-200mV-/160573836894?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item2562f24e5eHave you tried eBay? The above link is only an example...

author: microbug
author_rank: Frequent Contributor
timestamp: September 07, 2013, 11:08:45 am
content: Yes, I did check eBay - and although that panel meter looks good quality, it does not have an adjustable decimal point, like most of the other ones I found.

author: mickpah
author_rank: Regular Contributor
timestamp: September 07, 2013, 11:25:41 am
content: Sure Electronics - usually found on ebaydirect linkhttp://www.sureelectronics.net/category.php?id=110

author: rdl
author_rank: Super Contributor
timestamp: September 07, 2013, 03:01:24 pm
content: I realize you're not in America, but check around for this UP8135 meter. I have a couple and they work fine. 2 volt or 200 mV input with selectable decimal point. Maybe this would work for your power supply.http://www.ebay.com/itm/230363049931

author: miceuz
author_rank: Frequent Contributor
timestamp: September 07, 2013, 04:26:58 pm
content: If mechanical constrains allow it, I would just roll my own. A 7 segment display, a micro with ADC, a couple of resistors and full control you need.