Waveform Generator for up to ~50V? - Page 1
Forum section: electronics / projects

author: excitedbox
author_rank: Regular Contributor
timestamp: August 05, 2019, 06:28:29 am
content: For my printer project I need to be able to generate trapezoidal waveforms with fast rise and fall times up to 40V and short current spikes up to 7A if all nozzles are firing.Some print heads only need 19-23V while some piezo printheads need much higher but all need short pulses with rise and fall times of around 2-4 us and dwell times of around 10-20us. Most of the print heads will be completely in the positive V range but some will need to drop into the negative voltage.My question is would the fy6900 be good enough if I combined both channels in series to get to a max of 48V or would I be better off using any function generator or DAC and building my own amplifier with an op amp and some mosfets? I would like to be able to use the same setup for as much of my testing as possible and only make minor changes if not all configuration in software.I want to test around 10-15 print heads and since there is no real information available online I can not group them to use similar voltages and need my test setup as flexible as possible. I also need to be able to test many waveforms once I settle on 1 printhead to adjust for the 4 inks I will be using.

author: MosherIV
author_rank: Super Contributor
timestamp: August 05, 2019, 06:47:40 am
content: QuoteNo, you will not be able to use the fy6900 in that way.They will not like combining their outputs.They certainly cannot supply 7A.You could try builing an amplifier but again not really suited to the task.What you want is a power supply with controllable voltage output.

author: excitedbox
author_rank: Regular Contributor
timestamp: August 05, 2019, 07:41:57 am
content: I have seen one of those 30v generators combining 2 channels into 1 with a 60v p-p. Is the current limit too low for the fy6900? Ok yea it seems max output is 10watts for the whole thing. I guess I would be able to drive 1-2 nozzles at a time.I have found an Amplifier just now that could work for 31euros using a high voltage op amp. Then you use a +- power supply and a function generator to produce the output I need. People posted that they got over 12V/us slew rates which should be good enough.The problem with a programmable power supply is that the rise and fall speed is way too slow. I have looked at SMUs too and everything is in the ms range so much too slow for my needs.https://www.aliexpress.com/item/32864391386.html?scm=1007.22893.125764.0&pvid=1d8f27b5-f0e3-4d69-a153-7594aa872dd6&onelink_thrd=0.0&onelink_page_from=ITEM_DETAIL&onelink_item_to=32864391386&onelink_duration=0.958646&onelink_status=noneresult&onelink_item_from=32864391386&onelink_page_to=ITEM_DETAIL&aff_platform=promotion&cpt=1564986897424&sk=ZrRbaAe&aff_trace_key=aab2c62c46804ae6b49d2e7d94487c1a-1564986897424-08964-ZrRbaAe&terminal_id=fe13e8d3cbea4d58af3b60900cf8e9aa

author: mikerj
author_rank: Super Contributor
timestamp: August 05, 2019, 08:31:33 am
content: Quote from: excitedbox on August 05, 2019, 07:41:57 amThe FY6900, as with almost all signal generators, has a 50 ohm output. It can't provide anything like the kind of currents you need.Quote from: excitedbox on August 05, 2019, 07:41:57 amWhy are you looking at linear amplifiers to drive these print heads? Do you need to provide a non-digital waveform to drive then e.g. sinusoidal?

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: August 05, 2019, 08:38:50 am
content: hmmm... 40 Vpeak seems to be in the range of 200 W @ 4 Ohms or 100 W @ 8 Ohms HIFI amplifiers. maybe you can re-purpose one of those, remove the slew-rate limiter (if even necessary) and then feed it with a signal generator? the "better ones" in the good ole days of hifi were sometimes marketed with BW well beyond 100 kHz. could be juuust enough.don't know about the peak current handling capabilities, though.

author: StillTrying
author_rank: Super Contributor
timestamp: August 05, 2019, 03:02:26 pm
content: Rather thancreating+ve pulses up to 40V these things are always easier if you can arrange tosinktheon timecurrent instead, you could power 8 nozzels with one of these uln2803 darlington drivers, then the input simplifies to almost any pulse generator (even a 555!), and the +ve power supply simplifies to almost any 20-40V DC supply.www.ti.com/lit/gpn/uln2803aI think creating one output circuit that does both heat nozzels and piezo electric nozzels would be very difficult.https://en.wikipedia.org/wiki/Inkjet_printing

author: David Hess
author_rank: Super Contributor
timestamp: August 06, 2019, 04:25:24 am
content: 2 to 4 microsecond transition times require in the range of 100 to 200 kHz of bandwidth minimum so certainly feasible with a relatively simple push-pull linear amplifier. 40 volts at 7 amps is about a 6 ohm load so other than higher bandwidth than an audio amplifier, nothing special is required.

author: SiliconWizard
author_rank: Super Contributor
timestamp: August 06, 2019, 02:57:25 pm
content: Yes, I guess a relatively simple and low part count design around some kind of high-voltage opamp (such as the OPA454) followed by a push-pull output stage should be able to do it.

author: StillTrying
author_rank: Super Contributor
timestamp: August 06, 2019, 03:20:25 pm
content: "short current spikes up to 7A if all nozzles are firing."As I understand it from the 1st post, the up to 7A is the total current when a whole column of nozzles is firing, no individual nozzle would need a 7A driver.