Voltage to Current Module - Page 1
Forum section: electronics / beginners

author: Dado87
author_rank: Newbie
timestamp: July 06, 2016, 05:47:19 pm
content: Hi everyone,I want to make 4-20mA signal output from Arduino microcontroller (0-5V to 4-20mA). To do this I bought cheap module from ebay (http://www.ebay.de/itm/Voltage-to-Current-Signal-Transmitter-0-3-3-5-10-15V-to-4-20mA-Linear-conversion-/291658069232?hash=item43e82cf4f0:g:s6wAAOSw3KFWf0EI). But I have troubles to make it work... I did folowing circuit (https://postimg.org/image/vy524v8k1/). What Im doing wrong? My ampmeter is all time showing very low values (0-0,3mA).Thank you for any suggestion.Regards,Damir

author: modernjack3
author_rank: Contributor
timestamp: July 06, 2016, 05:49:54 pm
content: Hello , could you tell me what u Need the current thingy for if you could just use the Volts ? :/I know ist not a real answer but I am curious..

author: MosherIV
author_rank: Super Contributor
timestamp: July 06, 2016, 05:57:20 pm
content: HiSorry, we need to know the circuit of the module you bought to understand if you interfaced to it correctly. There did not look like there was any additiinal information on the ebay page.What happens if you disconnect Vout ?

author: Signal32
author_rank: Frequent Contributor
timestamp: July 06, 2016, 06:02:22 pm
content: Seems ok, so your circuit should work.Here is what to try:- Do the LED's turn on ?- Play around with the pots see that they're not causing the issue.- Don't short the output, put a 100R resistor in series.- If you're using a multimeter, make sure the probes are plugged in correctly

author: Dado87
author_rank: Newbie
timestamp: July 06, 2016, 07:50:58 pm
content: Hi Guys,I need current signal for control of pressure regulator (MPPE from Festo). Type I have needs to be controled with 4-20mA.There is no datasheet...but because of there many those modules on ebay I tought that just common way to transform V to I.Answears to Signal321.Yes, LED is turned on (both of them. with turning of pot one LED light more intense.2. If I take away pot and use 5V as Vin...the issue is steel there.3. I tryed with resistor...(220R, 100R, 50R) ...no change4. Multimeter should be connected correctly.MosherIV:If I disconect Vout then measured current is jumping around value of 5mA.

author: Signal32
author_rank: Frequent Contributor
timestamp: July 06, 2016, 07:54:20 pm
content: Try to post a hi-res picture of the front & back of the PCB.

author: MosherIV
author_rank: Super Contributor
timestamp: July 06, 2016, 08:07:46 pm
content: QuoteIs that better (it is specified as 4 to 20mA)?Does the current vary with the Vin (adjust the pot) now?Are you sure the module is only powered by the single Vcc pin?BTW If you want to try and build a circuit for yourself, watch thisSubstitute the precision volt with your pot voltage, adjust the current shunt value for something appropriate for 4 to 20mA (use ohms law to work out value)Only if you want to try that is.

author: Dado87
author_rank: Newbie
timestamp: July 06, 2016, 08:29:21 pm
content: Photos:I couldnt make better ones...on big IC on upper side stays: ST GZTH403 (above that is also number 324)...IC on bottom is ST 78M05 A 508some other links to similar product:http://www.ebay.de/itm/Voltage-to-Current-0-5V-to-4-20mA-Conversion-Module-for-Arduino-/262495219570?hash=item3d1def2f72http://de.aliexpress.com/item/AO-module-voltage-conversion-current-module-signal-conversion-0-2-5V-3-3V-5V-10V-15V/32657240669.html?spm=2114.010208.3.132.ZVeEwT&ws_ab_test=searchweb201556_10,searchweb201602_1_10037_10017_407_10033_406_10032,searchweb201603_7&btsid=bfdb43fc-ea89-4dcb-917e-2d466d896c27

author: MosherIV
author_rank: Super Contributor
timestamp: July 06, 2016, 08:55:40 pm
content: HiThe other links shows something interresting.Your diagram shows both Vin and Vout but the pictures show the module only has Vout.I think Vout is where you inject the pot voltage.I think the 2 pots are for adjusting the 4mA min and possibley the gain

author: Dado87
author_rank: Newbie
timestamp: July 06, 2016, 09:01:44 pm
content: I did mistake in my sketch...Insted of Vout is GND there...So my modul has Vin, GND and Vcc, Iout and GND on other side.

author: retrolefty
author_rank: Super Contributor
timestamp: July 06, 2016, 09:20:07 pm
content: Most industrial E/I convertors require a minimum 'loop voltage' to work correctly, usually they rate to like 12 to 40vdc loop voltage. 9 volts my not cut it.

author: MosherIV
author_rank: Super Contributor
timestamp: July 06, 2016, 09:21:07 pm
content: What happens if you short Vin to Gnd?What happens if you connect Vin to the battery?

author: Dado87
author_rank: Newbie
timestamp: July 06, 2016, 09:31:50 pm
content: retrolefty, I tryed with 18V DC source but...the same